Physical and Chemical Stability of Buffered Articaine: An In-Vitro Study

Physical and Chemical Stability of Buffered Articaine: An In-Vitro Study | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Physical and Chemical Stability of Buffered Articaine: An In-Vitro Study Ashwin Rao, Sushmitha P, Sudheer Moorkoth, Ashutosh Gupta, Srikant N, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7195283/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Objective: There is a lack of scientific data on the shelf-life of buffered articaine solutions. This study evaluated the physical and chemical stability of buffered 4% articaine with 1:100,000 epinephrine. Materials and Methods: For the study of physical stability, two groups (1P, 2P) (“P” designating samples to study physical stability) of triplet samples were prepared. The 1P samples were stored at 8 °C, and the 2P samples were stored at 25°C. The samples were evaluated every hour till 8 hours by inspecting the appearance of particulate matter against a black background, color change against a white background and pH using a calibrated pH meter. For the study of chemical stability, 4 groups (1C, 2C, 3C and 4C) (“C” designating samples to study chemical stability ) of triplet samples were prepared. 1C and 2C were used to evaluate the stability of articaine stored at 8°C and 25°C. 3C and 4C were used to evaluate the stability of epinephrine stored at 8°C and 25°C,respectively. The samples were evaluated every hour till 8 hours using a validated high-performance liquid chromatography method. Independent tests were applied for statistical analysis. Results : All the test samples remained colorless and clear for a period of 8 hours. The pH significantly increased from baseline at both 8°C and 25°C every hour until8 hours but remained within the acceptable physiological pH. There was no significant degradation in the concentration of buffered articaineafter 8 hours at either 25°C or 8°C. However, the concentration of epinephrine significantly decreased at every test interval after 1 hour at 25°C ( p = 0.002)and after 2 hours at 8°C ( p = 0.038). Conclusion : The buffered articaine solution remained physically stable at 8 hours. The buffered articaine solution remained chemically stable at 8 hours at 8°C and 25°C. Epinephrine remained chemically stable for 2 hours at 8°C and 1 hour at 25°C. Health sciences/Health care/Dentistry/Dental treatments Health sciences/Health care/Dentistry articaine sodium bicarbonate buffering alkalinization Figures Figure 1 Figure 2 Figure 3 Figure 4 1. Introduction Pain management is a critical aspect of patient care in dentistry [ 1 ]. Local anesthesia is an important tool in this regard. Various methods have explored ways to increase the efficacy of local anesthesia. Alkalizing the anesthetic cartridge is one such method [ 2 ]. Local anesthetic solutions are acidified to increase their stability and solubility during storage [ 3 ]. However, a low pH results in a high percentage of charged molecules. These molecules, when deposited into the tissues surrounding the nerves, often lead to a burning sensation. They also delay the onset of action [ 3 ]. Buffering the local anesthetic solution can potentially decrease the burning sensation during injection, quicken the onset of action and provide more profound anesthesia. This is due to the increased pH of the solution and a 6000-fold increase in the number of active molecules [ 4 ]. Four percent articaine hydrochloride has steadily gained popularity among dental practitioners [ 5 ]. Studies have shown that buffered articaine is a significantly better anesthetic agent than unbuffered articaine with patients reporting less pain during the injection [ 6 ]. Despite these advantages, buffered articaine has not been used routinely in dental practice. This could be due to its perceived, short shelf life and instability of the solution, which may require it to be freshly prepared each time before injection. This process can consume clinical time [ 7 ]. However, scientific data on the shelf-life and stability of buffered articaine are lacking. This in vitro study therefore aimed to evaluate the physical and chemical stability of a buffered 4% articaine solution with 1:100,000 epinephrine. 2. Methodology 2A Physical Stability Study 8.4% sodium bicarbonate solution (Samarth Life Sciences Pvt. Ltd., Maharashtra, India) was used as the buffering agent. From the 1.7 ml cartridge containing 4% articaine hydrochloride solution (Septanest, Septodont Healthcare, India Pvt. Ltd., Maharashtra, India), 0.17 ml of solution was discarded to create space for the buffering solution. A total of 0.17 ml (17 units) of 8.4% sodium bicarbonate was withdrawn with an insulin syringe (Dispo Van Insulin syringe Super Fine 31G short needle, Hindustan Syringes and medical device Ltd., Faridabad, India). This solution was added to the cartridge. The final solution contained 4% articaine hydrochloride with 1:100,000 epinephrine and 8.4% sodium bicarbonate at a ratio of 10:1 [ 8 , 9 ]. Two groups of triplet samples were prepared for analysis. Group 1P (“P” designating samples prepared to study physical stability) samples were used for the evaluation of the physical stability of the solution when stored in the refrigerator at 8°C. The Group 2P samples were used for the evaluation of the physical stability of the solution stored at room temperature at 25°C protected from sunlight. The samples were evaluated at 0, 1, 2, 3, 4, 5, 6, 7 and 8 hours. During each sampling hour, the investigator inspected each sample for the appearance of particulate matter against a black background and for color change against a white background. The pH was determined at each sampling hour via a pH meter (ELICO pH meter, ELICO R, Hyderabad, Telangana) calibrated between 4 and 9. 2B Chemical Stability Study: The chemical stability of both articaine and epinephrine was analyzed via validated high-performance liquid chromatography (HPLC) methods. A Shimadzu Ultra-Fast Liquid chromatography system (Shimadzu corporation, Kyoto, Japan) was used for the purpose. Chemical stability was evaluated by measuring and comparing the decrease in concentration or degradation of the drug at each sampling hour. The analytical system consisted of an isocratic pump, a photodiode array detector, and an autoinjector coupled with a sample cooler set at 4°C. Lab solution software was used for data collection and analysis. Development of a validated HPLC method for determination of articaine and epinephrine Development and validation of an HPLC method involved the creation of a chromatographic method that can specifically and reliably detect a drug and its degradation products [ 10 ]. A stability-indicating HPLC method suitable for determining both articaine and epinephrine simultaneously was developed and validated. A stock solution of articaine hydrochloride solution was prepared by adding 1 mg of articaine (Sigma Aldrich, St. Louis, MO, USA) in 1 mL of water to achieve a final concentration of 1 mg/ml. The prepared stock solution was used for serial dilution to achieve solutions with the desired concentrations of 0.5, 1, 2, 4, 8, 12, 16, and 20 µg/ml. Stock solutions of 1.0 mg/mL epinephrine were prepared by adding 1 mg of epinephrine (Sigma Aldrich, St. Louis, MO, USA) to 1 ml of water. Aliquots were taken and diluted with the mobile phase to obtain the required concentration of 0.25 µg/mL. The mobile phase used was phosphate buffer (pH 3.1) containing 0.1% triethyl alcohol and methanol. Both samples were filtered through a polytetrafluoroethylene syringe filter before HPLC analysis. A gradient elution was performed on a C18 column. The separation was carried out at a flow rate of 1 mL/min, with a column oven temperature of 25°C and an injection volume of 10 µL. Detection was performed using a photodiode array (PDA) detector at 279 nm, with a total runtime of 13 minutes. The final analytical method for the simultaneous quantification of articaine and epinephrine is given in Table 1 , and the gradient program is given in Table 2 . The method effectively separates and quantifies articaine and epinephrine with good resolution, sensitivity, and reliability. Table 1 Final analytical methods for the simultaneous quantification of articaine and epinephrine Column C 18 column Mobile Phase Phosphate buffer ph 3.1 + 0.1% TriethylAlcohol and Methanol Mode Gradient program Column oven Temperature 25°C Inj vol 10 µl Detector used Photodiode array (PDA) detector Wavelength used 279 Mobile phase flow rate 1 mL/min Runtime 13 min Table 2 Gradient program for the simultaneous quantification of articaine and epinephrine Sl. no. Time Pump Buffer concentration 1. 0.01 Pump B 95 2. 3.00 Pump B 95 3. 4.00 Pump B 40 4. 7.00 Pump B 40 5. 8.00 Pump B 95 6. 13.00 Pump B 95 7. 13.10 Stop The developed HPLC method was then validated as per “The International Council for Harmonization of Technical Requirements for Pharmaceuticals for Human Use (ICH)” guidelines [ 11 ]. The validation parameters were specificity, selectivity, limit of detection (LOD), limit of quantification (LOQ), linearity, accuracy, and precision (interday and intraday). The HPLC gradient program used during the analysis specifically showed changes in Pump B (buffer or organic solvent concentration) over time, as shown in Table 2 . This type of gradient elution helps achieve clear separation of different compounds (articaine and epinephrine) by changing the solvent strength over time. Preparation of the admixture for analysis : A total of 1.7 ml of the commercially available injectable articaine cartridge consists of 68 mg of articaine and 0.017 mg of epinephrine. It was diluted with the mobile phase until a 9-µg concentration of articaine was achieved. Later, in a microcentrifuge tube, 1 ml of the diluted 4% articaine hydrochloride was dispensed, from which 0.1 ml was withdrawn. Then, 0.1 ml of 8.4% sodium bicarbonate was added back to the articaine solution. Thus, the final test admixture contained 4% articaine hydrochloride with 1:100,000 epinephrine and 8.4% sodium bicarbonate at a ratio of 10:1. Four groups of triplet samples each were prepared for analysis. Group 1C (“C” designating samples prepared to study chemical stability) samples were used for the evaluation of the stability of articaine when stored in the refrigerator at 8°C. The Group 2C samples were used to evaluate the stability of articaine at room temperature (25°C), which is protected from sunlight. The Group 3C samples were used to evaluate the stability of epinephrine when stored at 8°C, and the Group 4C samples were used to evaluate the stability of epinephrine when the samples were stored at 25°C. The samples were evaluated at 0, 1, 2, 3, 4, 5, 6, 7 and 8 hours. These samples were injected into the HPLC column at every sampling hour. The samples were assayed in triplicate after visual inspection for any precipitation. 3. Statistical Analysis Independent t tests were applied to compare changes in pH and the chemical stability of the buffered articaine and epinephrine samples stored at 8°C and 25°C. The significance was set at p < 0.05. 4. Results 4A. Development and validation of the stability of the HPLC method : The final chromatograms for articaine and epinephrine are shown in Fig. 1 . The chromatogram shows the successful separation of articaine and epinephrine under optimized HPLC conditions. Epinephrine elutes at a retention time (Rt) of 2.94 minutes, whereas articaine elutes later at 9.70 minutes, indicating effective resolution between the two compounds. The sharp and well-defined peaks suggest that the method is suitable for simultaneous analysis, likely intended for quality control or validation of pharmaceutical formulations containing both analytes. The developed HPLC method demonstrated effective separation and reliable quantification of epinephrine (Rt = 2.94 ± 0.013 min) and articaine (Rt = 9.79 ± 0.035 min), with a resolution of 6.84 ± 0.04 and no interfering peaks, confirming its specificity. Both analytes showed good peak shapes (tailing factor < 1.5) and high column efficiency, with theoretical plates exceeding 5800. The method exhibited excellent linearity over a concentration range of 0.5–20 µg/mL (r² ≥ 0.997), and low LOD and LOQ values (125 ng/mL and 250 ng/mL, respectively) for both the analytes. The accuracy was within acceptable limits, with recoveries ranging from 95.55–100.89%, and precision was confirmed by low %CVs in both the repeatability and interday presion studies. Stability testing indicated minimal degradation under bench-top and autosampler conditions, supporting the robustness of the method. Validation data of the optimized analytical method for articaine and epinephrine are given in Table 3 . Table 3 Validation data of the optimized analytical method for articaine and epinephrine Parameters Epinephrine Articaine Retention time (min) 2.94 ± 0.013 9.79 ± 0.035 Tailing factor 1.25 ± 0.01 1.31 ± 0.01 Theoretical plate 5858.92 ± 34.22 8153.16 ± 123.96 Specificity No interfering peaks at the tR of epinephrine and articaine Resolution 6.84 ± 0.04 Linearity range (µg/mL) 0.5–20 0.5–20 Regression equation y = 4667.9x − 2357 y = 18441x − 1477.4 Correlation coefficient (r 2 ) 0.997 0.999 LOD (ng/mL) 125 125 LOQ (ng/mL) 250 250 Accuracy (% Recovery) 80% 96.09 99.05 100% 97.69 100.89 120% 95.55 98.85 Precision (% CV) Repeatability 0.81 0.15 Interday 1.39 0.13 Stability (% change) Bench-top -1.21% 0.45 Autosampler -0.91% 1.34 4B. Physical compatibility: All the test samples remained colorless and clear when observed against a white background. No samples presented any particulate matter or suspension when viewed against a black background. The pH significantly increased from baseline at both 8°C and 25°C (Table 4 ) every hour until 8 hours but remained within the acceptable physiologic pH range of 7.35–7.45 [ 12 ]. There was no statistically significant difference between the increases in pH compared with the baseline at 8°C and 25°C at any time interval until 8 hours (Fig. 2 ). The only exception was at 2 hours, where the difference was significant ( p = .018). Table 4 Comparison of pH values between the baseline and each hour at 8°C and 25°C Time Interval n Mean pH ± SD Mean Difference ± SD t value p value 8 degrees Baseline 3 7.05 ± 0.05 – – – 1 hour 3 7.12 ± 0.08 -0.07 ± 0.03 -4.04 0.056 2 hours 3 7.17 ± 0.04 -0.12 ± 0.02 -10.26 0.009 3 hours 3 7.19 ± 0.06 -0.14 ± 0.01 -24.25 0.002 4 hours 3 7.27 ± 0.06 -0.22 ± 0.01 -38.11 0.001 5 hours 3 7.38 ± 0.03 -0.33 ± 0.02 -28.58 0.001 6 hours 3 7.41 ± 0.05 -0.36* – – 7 hours 3 7.43 ± 0.07 -0.38 ± 0.02 -32.91 0.001 8 hours 3 7.45 ± 0.08 -0.40 ± 0.03 -23.09 0.002 25 degrees Baseline 3 7.06 ± 0.05 – – – 1 hour 3 7.20 ± 0.02 -0.14 ± 0.05 -4.80 0.041 2 hours 3 7.26 ± 0.02 -0.20 ± 0.03 -12.20 0.007 3 hours 3 7.29 ± 0.02 -0.23 ± 0.04 -9.71 0.010 4 hours 3 7.32 ± 0.01 -0.26 ± 0.04 -12.05 0.007 5 hours 3 7.33 ± 0.02 -0.27 ± 0.04 -12.51 0.006 6 hours 3 7.38 ± 0.01 -0.32 ± 0.04 -12.72 0.006 7 hours 3 7.41 ± 0.02 -0.35 ± 0.04 -14.86 0.004 8 hours 3 7.42 ± 0.02 -0.36 ± 0.03 -21.80 0.002 * t value cannot be calculated due to the same standard deviation in both the baseline and 6 hour values 4C. Chemical Stability: There was no significant degradation in the concentration of buffered articaine after 8 hours at either 8°C or 25°C (Table 5 ). There was also no significant difference when the degradation at 25°C and 8°C was compared (Fig. 3 ) at each sampling hour from the baseline. Therefore, articaine remained chemically stable at both 25°C and 8°C for 8 hours. However, the concentration of epinephrine significantly decreased at every test interval after 1 hour at 25°C ( p = 0.002) (Table 6 ) and after 2 hours at 8°C ( p = 0.038) (Table 6 ). Table 5 Concentrations of articaine at each sampling hour compared with the baseline at 8°C and 25°C Time Interval n Mean % assay ± SD Mean Difference ± SD t value p value 8 degrees Baseline 3 95.78 ± 1.15 – – – 1 hour 3 95.64 ± 1.00 0.14 ± 0.18 1.36 0.306 2 hours 3 95.41 ± 1.01 0.36 ± 0.19 3.27 0.082 3 hours 3 95.02 ± 1.37 0.76 ± 0.47 2.80 0.107 4 hours 3 94.46 ± 1.55 1.32 ± 0.59 3.89 0.060 5 hours 3 93.30 ± 0.28 2.48 ± 1.41 3.05 0.093 6 hours 3 93.06 ± 0.37 2.72 ± 1.52 3.10 0.090 7 hours 3 92.84 ± 0.36 2.93 ± 1.50 3.39 0.077 8 hours 3 92.61 ± 0.53 3.16 ± 1.52 3.60 0.069 25 degrees Baseline 3 94.95 ± 0.54 – – – 1 hour 3 94.11 ± 1.11 0.84 ± 1.04 1.40 0.297 2 hours 3 93.85 ± 1.18 1.10 ± 1.09 1.76 0.221 3 hours 3 93.77 ± 1.15 1.19 ± 1.09 1.89 0.200 4 hours 3 93.72 ± 1.17 1.23 ± 1.11 1.92 0.195 5 hours 3 93.52 ± 1.21 1.43 ± 1.07 2.32 0.146 6 hours 3 93.44 ± 1.27 1.51 ± 1.13 2.32 0.146 7 hours 3 93.24 ± 1.25 1.71 ± 1.01 2.92 0.100 8 hours 3 93.19 ± 1.20 1.76 ± 0.97 3.14 0.088 * t value cannot be calculated due to the same standard deviation in both the baseline and 6 hour values Table 6 Concentration of epinephrine at each sampling hour compared with that at baseline at 8°C and 25°C Time Interval n Mean ± SD Mean Difference ± SD t value p value 8 degree Baseline 3 98.63 ± 1.34 – – – 1 hour 3 97.30 ± 0.77 1.33 ± 0.65 3.52 0.072 2 hours 3 96.31 ± 0.84 2.32 ± 1.36 2.95 0.098 3 hours 3 95.78 ± 0.81 2.85 ± 1.00 4.95 0.038 4 hours 3 95.40 ± 0.62 3.22 ± 0.75 7.41 0.018 5 hours 3 94.89 ± 0.95 3.74 ± 0.70 9.26 0.011 6 hours 3 94.37 ± 1.18 4.26 ± 1.09 6.78 0.021 7 hours 3 94.01 ± 1.24 4.62 ± 1.28 6.26 0.025 8 hours 3 93.63 ± 1.29 5.00 ± 1.51 5.75 0.029 25 degree Baseline 3 97.62 ± 0.38 – – – 1 hour 3 97.38 ± 0.57 0.23 ± 0.19 2.06 0.176 2 hours 3 97.19 ± 0.40 0.42 ± 0.03 23.67 0.002 3 hours 3 96.63 ± 0.30 0.99 ± 0.43 4.01 0.057 4 hours 3 96.27 ± 0.19 1.35 ± 0.52 4.51 0.046 5 hours 3 96.04 ± 0.22 1.57 ± 0.60 4.56 0.045 6 hours 3 95.59 ± 0.41 2.03 ± 0.79 4.46 0.047 7 hours 3 95.19 ± 0.42 2.43 ± 0.79 5.32 0.034 8 hours 3 94.29 ± 0.8 3.33 ± 0.88 6.55 0.022 * t value cannot be calculated due to the same standard deviation in both the baseline and 6 hour values Discussion Buffering or, more appropriately, alkalinization is the process of adding a basic solution to an acidic solution such as a commercially available local anesthetic solution [ 13 ]. This study examined the physical and chemical stability of a 4% buffered articaine solution with 1:100,000 epinephrine. We studied the stability of epinephrine along with 4% articaine because epinephrine is an integral part of any local anesthetic solution and has numerous clinical advantages [ 14 ]. The solutions were evaluated for 8 hours to complement the average duration of clinical functioning. The solutions were tested at two temperatures, 25°C and 8°C, to provide recommendations on the mode of storage of the buffered articaine solution. A 10:1 dilution with 8.4% sodium bicarbonate was used to assess physical stability. The amount of basic solution must be specified because an excess amount will cloud and precipitate the local anesthetic solution [ 13 ]. A validated HPLC method was used for the study of chemical stability [ 13 ]. The articaine samples containing epinephrine were physically stable throughout the test period at both temperatures. They remained clear, colorless and devoid of particulate matter on examination. There were also no significant changes in pH. Similar results have been published with respect to the physical stability of lidocaine by various authors [ 15 , 16 ]. This study provides similar data for articaine. All the buffered articaine samples retained at least 92.61% and 93.19% of the original concentration at 8°C and 25°C, respectively. We measured the concentrations only for 8 hours, unlike previous studies that measured the stability of lidocaine for periods of up to 7 days [ 9 ]. We rationalized that preparing fresh solutions at the beginning of each working day is feasible in any practice. This is especially important until we obtain more long-term data on buffered articaine solutions. Epinephrine significantly decreased in concentration, i.e., 93.63% and 94.28% of the initial concentration at both 8°C and 25°C, respectively, at 8 hours. Epinephrine 4-[1R)-1-(3,4-dihydroxyphenyl)-2-(methylamino) ethanol] is an injectable solution that contains catecholamines. These catecholamine-containing injectable solutions are unstable under alkaline environments and at high temperatures, primarily because the oxidation of catecholamines promotes their breakdown [ 17 ]. The nature and effect of the degradation products of epinephrine-containing articaine injectables require further research. The limitation of this study is that these results cannot be extrapolated to assign expiration dates to buffered articaine solutions with epinephrine in actual clinical settings. This study addresses only one aspect of buffered articaine, namely, its shelf life, and does not address its clinical effectiveness. Future studies should focus on the clinical efficacy of buffered articaine with epinephrine stored for various time intervals at varying temperatures. Conclusion Under the conditions of the study, we can draw the following conclusions: Four percent articaine with 1:100,000 epinephrine remained physically stable for 8 hours at 8°C and 25°C. Four percent articaine remained chemically stable in terms of concentration at both 25°C and 8°C for 8 hours. Epinephrine significantly decreased in concentration at every test interval after 1 hour at 25°C and after 2 hours at 8°C. Declarations Conflict of interest: Nil Acknowledgements: Nil Data Availability statement: The original data is available with the corresponding author and can be shared on request. Ethics: Institutional Ethics Committee approval was obtained from Manipal College of Dental Sciences, Mangalore (Protocol reference number: 22089). Source of Funding: The authors received no specific funding for this work. Authors' contributions: SP, SM, AG and AR were responsible for the concept, data acquisition, drafting the article, revision and final approval. 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Buffered lidocaine hydrochloride solution with and without epinephrine: stability in polypropylene syringes. The Canadian journal of hospital pharmacy. 2009;62(5):375. Donnelly RF. Stability of buffered lidocaine in glass vials. The Canadian Journal of Hospital Pharmacy. 2011;64(4):289. Hoellein L, Holzgrabe U. Ficts and facts of epinephrine and norepinephrine stability in injectable solutions. Int J Pharm. 2012;434(1–2):468–80. Additional Declarations There is no conflict of interest Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-7195283","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":492435707,"identity":"8cdad151-4a19-4514-af68-20f11964ab20","order_by":0,"name":"Ashwin Rao","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA+0lEQVRIiWNgGAWjYFACHgaGBDCD+QCQkGBgYIcIEqOFLQGihZkYLVCGAYQmpIW//+wxiYc7GPL523u+bvi5wyKPv5mB8cHbNtxaJG7kpUkknmGwnHHm7LabvWckiiUOMzAbzsWjheEGj9mNxDYGA4Ybudtu8LZJJDYcZmCT5sWjRf78GYgW+Rs5z27+BWqZf5iB/Tc+LQYHciBaDG7ksN0G2bIBaAszPi2GN3LMfyS2SRgYnjlmdlu2TaLY8DBjs+Scc7i1yJ0/Y2z4s83GQO5487Obb9vq8oCMgx/elOHxPgRIwFkJDAyMDQTVo4AE0pSPglEwCkbBSAAANV5SDoSf4gEAAAAASUVORK5CYII=","orcid":"https://orcid.org/0000-0002-7983-0773","institution":"DEPARTMENT OF PEDIATRIC AND PREVENTIVE DENTISTRY MANIPAL COLLEGE OF DENTAL SCIENCES MANGALORE MANIPAL ACADEMY OF HIGHER EDUCATION (MAHE), MANIPAL,KARNATAKA, INDIA","correspondingAuthor":true,"prefix":"","firstName":"Ashwin","middleName":"","lastName":"Rao","suffix":""},{"id":492435708,"identity":"72d1498e-bfba-4488-b68d-22880ca9f432","order_by":1,"name":"Sushmitha P","email":"","orcid":"","institution":"FORMER POST GRADUATE STUDENT, DEPARTMENT OF PEDIATRIC AND PREVENTIVE DENTISTRY, MANIPAL COLLEGE OF DENTAL SCIENCES MANGALORE MANIPAL ACADEMY OF HIGHER EDUCATION (MAHE), MANIPAL","correspondingAuthor":false,"prefix":"","firstName":"Sushmitha","middleName":"","lastName":"P","suffix":""},{"id":492435709,"identity":"00a1e469-b368-4a48-8202-0270ac97321e","order_by":2,"name":"Sudheer Moorkoth","email":"","orcid":"","institution":"Manipal College of Pharmaceutical Sciences, Manipal Academy of Higher Education,Manipal, Karnataka,India","correspondingAuthor":false,"prefix":"","firstName":"Sudheer","middleName":"","lastName":"Moorkoth","suffix":""},{"id":492435710,"identity":"26efc147-fc97-478f-8b90-228526854852","order_by":3,"name":"Ashutosh Gupta","email":"","orcid":"","institution":"Manipal College of Pharmaceutical Sciences, Manipal Academy of Higher Education,Manipal, Karnataka,India","correspondingAuthor":false,"prefix":"","firstName":"Ashutosh","middleName":"","lastName":"Gupta","suffix":""},{"id":492435711,"identity":"d6dd15d5-0ed4-496d-ab53-c743dd21f6ed","order_by":4,"name":"Srikant N","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Srikant","middleName":"","lastName":"N","suffix":""},{"id":492435712,"identity":"e8e526f0-2c42-4dd5-84e6-f56c313a60d3","order_by":5,"name":"Karuna Yarmunja Mahabala","email":"","orcid":"https://orcid.org/0000-0002-7504-1021","institution":"Manipal College of Dental Sciences, Mangalore, Manipal Academy of Higher Education, Manipal.","correspondingAuthor":false,"prefix":"","firstName":"Karuna","middleName":"Yarmunja","lastName":"Mahabala","suffix":""},{"id":492435713,"identity":"20c5b8be-26d4-46ac-b1e4-d971914af55f","order_by":6,"name":"Anupama Nayak P","email":"","orcid":"https://orcid.org/0000-0001-7726-2525","institution":"Manipal College of Dental Sciences, Mangalore","correspondingAuthor":false,"prefix":"","firstName":"Anupama","middleName":"Nayak","lastName":"P","suffix":""}],"badges":[],"createdAt":"2025-07-23 10:28:45","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7195283/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7195283/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":88001688,"identity":"e3d2fdf5-4898-42e4-9b96-ab6a77c673de","added_by":"auto","created_at":"2025-07-31 10:24:16","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":27897,"visible":true,"origin":"","legend":"\u003cp\u003eChromatograms of articane (Rt 9.70 min) and epinephrine (2.94 min) obtained under the optimized conditions\u003c/p\u003e","description":"","filename":"Figure1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7195283/v1/a26c7872a43806a3b164e3d4.jpg"},{"id":88000036,"identity":"a272f77f-cb5b-476f-86d1-d0b573cd2dce","added_by":"auto","created_at":"2025-07-31 10:16:16","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":120816,"visible":true,"origin":"","legend":"\u003cp\u003eComparison between increases in pH at 8°C and 25°C\u003c/p\u003e","description":"","filename":"Figure2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7195283/v1/485559025fd100194df3d2e5.jpg"},{"id":88000039,"identity":"16669cbe-587c-4da3-8be0-cbaef744bcab","added_by":"auto","created_at":"2025-07-31 10:16:16","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":109051,"visible":true,"origin":"","legend":"\u003cp\u003eComparison of the degradation of articaine at 25°C and 8°C compared to baseline\u003c/p\u003e","description":"","filename":"Figure3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7195283/v1/637be7ca255c50ca4501cb19.jpg"},{"id":88000043,"identity":"6c9cc5ea-e9e9-47ab-8773-59082962604f","added_by":"auto","created_at":"2025-07-31 10:16:16","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":60609,"visible":true,"origin":"","legend":"\u003cp\u003eComparison of the degradation of epinephrine at 25°C and 8°C compared to baseline\u003c/p\u003e","description":"","filename":"Figure4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7195283/v1/d95a35c321977eabffb42901.jpg"},{"id":95527152,"identity":"d019339c-ed44-4226-82fb-93fe659db5d6","added_by":"auto","created_at":"2025-11-10 10:11:11","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1432374,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7195283/v1/c5d2357d-f023-4d61-9c4e-b833d90503f3.pdf"}],"financialInterests":"There is no conflict of interest","formattedTitle":"Physical and Chemical Stability of Buffered Articaine: An In-Vitro Study","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003ePain management is a critical aspect of patient care in dentistry [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. Local anesthesia is an important tool in this regard. Various methods have explored ways to increase the efficacy of local anesthesia. Alkalizing the anesthetic cartridge is one such method [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eLocal anesthetic solutions are acidified to increase their stability and solubility during storage [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. However, a low pH results in a high percentage of charged molecules. These molecules, when deposited into the tissues surrounding the nerves, often lead to a burning sensation. They also delay the onset of action [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eBuffering the local anesthetic solution can potentially decrease the burning sensation during injection, quicken the onset of action and provide more profound anesthesia. This is due to the increased pH of the solution and a 6000-fold increase in the number of active molecules [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eFour percent articaine hydrochloride has steadily gained popularity among dental practitioners [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. Studies have shown that buffered articaine is a significantly better anesthetic agent than unbuffered articaine with patients reporting less pain during the injection [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eDespite these advantages, buffered articaine has not been used routinely in dental practice. This could be due to its perceived, short shelf life and instability of the solution, which may require it to be freshly prepared each time before injection. This process can consume clinical time [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. However, scientific data on the shelf-life and stability of buffered articaine are lacking. This in vitro study therefore aimed to evaluate the physical and chemical stability of a buffered 4% articaine solution with 1:100,000 epinephrine.\u003c/p\u003e"},{"header":"2. Methodology","content":"\u003cp\u003e\u003cb\u003e2A Physical Stability Study\u003c/b\u003e\u003c/p\u003e\u003cp\u003e8.4% sodium bicarbonate solution (Samarth Life Sciences Pvt. Ltd., Maharashtra, India) was used as the buffering agent. From the 1.7 ml cartridge containing 4% articaine hydrochloride solution (Septanest, Septodont Healthcare, India Pvt. Ltd., Maharashtra, India), 0.17 ml of solution was discarded to create space for the buffering solution. A total of 0.17 ml (17 units) of 8.4% sodium bicarbonate was withdrawn with an insulin syringe (Dispo Van Insulin syringe Super Fine 31G short needle, Hindustan Syringes and medical device Ltd., Faridabad, India). This solution was added to the cartridge. The final solution contained 4% articaine hydrochloride with 1:100,000 epinephrine and 8.4% sodium bicarbonate at a ratio of 10:1 [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eTwo groups of triplet samples were prepared for analysis. Group 1P (\u0026ldquo;P\u0026rdquo; designating samples prepared to study physical stability) samples were used for the evaluation of the physical stability of the solution when stored in the refrigerator at 8\u0026deg;C. The Group 2P samples were used for the evaluation of the physical stability of the solution stored at room temperature at 25\u0026deg;C protected from sunlight. The samples were evaluated at 0, 1, 2, 3, 4, 5, 6, 7 and 8 hours.\u003c/p\u003e\u003cp\u003eDuring each sampling hour, the investigator inspected each sample for the appearance of particulate matter against a black background and for color change against a white background. The pH was determined at each sampling hour via a pH meter (ELICO pH meter, ELICO \u003csup\u003eR,\u003c/sup\u003e Hyderabad, Telangana) calibrated between 4 and 9.\u003c/p\u003e\n\u003ch3\u003e2B Chemical Stability Study:\u003c/h3\u003e\n\u003cp\u003eThe chemical stability of both articaine and epinephrine was analyzed via validated high-performance liquid chromatography (HPLC) methods. A Shimadzu Ultra-Fast Liquid chromatography system (Shimadzu corporation, Kyoto, Japan) was used for the purpose. Chemical stability was evaluated by measuring and comparing the decrease in concentration or degradation of the drug at each sampling hour. The analytical system consisted of an isocratic pump, a photodiode array detector, and an autoinjector coupled with a sample cooler set at 4\u0026deg;C. Lab solution software was used for data collection and analysis.\u003c/p\u003e\u003cp\u003e\u003cb\u003eDevelopment of a validated HPLC method for determination of articaine and epinephrine\u003c/b\u003e\u003c/p\u003e\u003cp\u003eDevelopment and validation of an HPLC method involved the creation of a chromatographic method that can specifically and reliably detect a drug and its degradation products [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. A stability-indicating HPLC method suitable for determining both articaine and epinephrine simultaneously was developed and validated. A stock solution of articaine hydrochloride solution was prepared by adding 1 mg of articaine (Sigma Aldrich, St. Louis, MO, USA) in 1 mL of water to achieve a final concentration of 1 mg/ml. The prepared stock solution was used for serial dilution to achieve solutions with the desired concentrations of 0.5, 1, 2, 4, 8, 12, 16, and 20 \u0026micro;g/ml. Stock solutions of 1.0 mg/mL epinephrine were prepared by adding 1 mg of epinephrine (Sigma Aldrich, St. Louis, MO, USA) to 1 ml of water. Aliquots were taken and diluted with the mobile phase to obtain the required concentration of 0.25 \u0026micro;g/mL. The mobile phase used was phosphate buffer (pH 3.1) containing 0.1% triethyl alcohol and methanol. Both samples were filtered through a polytetrafluoroethylene syringe filter before HPLC analysis. A gradient elution was performed on a C18 column. The separation was carried out at a flow rate of 1 mL/min, with a column oven temperature of 25\u0026deg;C and an injection volume of 10 \u0026micro;L. Detection was performed using a photodiode array (PDA) detector at 279 nm, with a total runtime of 13 minutes. The final analytical method for the simultaneous quantification of articaine and epinephrine is given in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, and the gradient program is given in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. The method effectively separates and quantifies articaine and epinephrine with good resolution, sensitivity, and reliability.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eFinal analytical methods for the simultaneous quantification of articaine and epinephrine\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"2\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eColumn\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eC\u003csub\u003e18\u003c/sub\u003e column\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eMobile Phase\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003ePhosphate buffer ph 3.1 + 0.1% TriethylAlcohol and Methanol\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eMode\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eGradient program\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eColumn oven Temperature\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e25\u0026deg;C\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eInj vol\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e10 \u0026micro;l\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eDetector used\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003ePhotodiode array (PDA) detector\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eWavelength used\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e279\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eMobile phase flow rate\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1 mL/min\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eRuntime\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e13 min\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eGradient program for the simultaneous quantification of articaine and epinephrine\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"4\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSl. no.\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eTime\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003ePump\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eBuffer concentration\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e1.\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e0.01\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003ePump B\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e95\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e2.\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e3.00\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003ePump B\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e95\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e3.\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e4.00\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003ePump B\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e40\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e4.\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e7.00\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003ePump B\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e40\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e5.\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e8.00\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003ePump B\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e95\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e6.\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e13.00\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003ePump B\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e95\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e7.\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e13.10\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eStop\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eThe developed HPLC method was then validated as per \u0026ldquo;The International Council for Harmonization of Technical Requirements for Pharmaceuticals for Human Use (ICH)\u0026rdquo; guidelines [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. The validation parameters were specificity, selectivity, limit of detection (LOD), limit of quantification (LOQ), linearity, accuracy, and precision (interday and intraday).\u003c/p\u003e\u003cp\u003eThe HPLC gradient program used during the analysis specifically showed changes in Pump B (buffer or organic solvent concentration) over time, as shown in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. This type of gradient elution helps achieve clear separation of different compounds (articaine and epinephrine) by changing the solvent strength over time.\u003c/p\u003e\u003cp\u003e\u003cb\u003ePreparation of the admixture for analysis\u003c/b\u003e:\u003c/p\u003e\u003cp\u003eA total of 1.7 ml of the commercially available injectable articaine cartridge consists of 68 mg of articaine and 0.017 mg of epinephrine. It was diluted with the mobile phase until a 9-\u0026micro;g concentration of articaine was achieved. Later, in a microcentrifuge tube, 1 ml of the diluted 4% articaine hydrochloride was dispensed, from which 0.1 ml was withdrawn. Then, 0.1 ml of 8.4% sodium bicarbonate was added back to the articaine solution. Thus, the final test admixture contained 4% articaine hydrochloride with 1:100,000 epinephrine and 8.4% sodium bicarbonate at a ratio of 10:1.\u003c/p\u003e\u003cp\u003eFour groups of triplet samples each were prepared for analysis. Group 1C (\u0026ldquo;C\u0026rdquo; designating samples prepared to study chemical stability) samples were used for the evaluation of the stability of articaine when stored in the refrigerator at 8\u0026deg;C. The Group 2C samples were used to evaluate the stability of articaine at room temperature (25\u0026deg;C), which is protected from sunlight. The Group 3C samples were used to evaluate the stability of epinephrine when stored at 8\u0026deg;C, and the Group 4C samples were used to evaluate the stability of epinephrine when the samples were stored at 25\u0026deg;C. The samples were evaluated at 0, 1, 2, 3, 4, 5, 6, 7 and 8 hours. These samples were injected into the HPLC column at every sampling hour. The samples were assayed in triplicate after visual inspection for any precipitation.\u003c/p\u003e"},{"header":"3. Statistical Analysis","content":"\u003cp\u003eIndependent t tests were applied to compare changes in pH and the chemical stability of the buffered articaine and epinephrine samples stored at 8\u0026deg;C and 25\u0026deg;C. The significance was set at \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05.\u003c/p\u003e"},{"header":"4. Results","content":"\u003cp\u003e\u003cb\u003e4A. Development and validation of the stability of the HPLC method\u003c/b\u003e:\u003c/p\u003e\u003cp\u003eThe final chromatograms for articaine and epinephrine are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. The chromatogram shows the successful separation of articaine and epinephrine under optimized HPLC conditions. Epinephrine elutes at a retention time (Rt) of 2.94 minutes, whereas articaine elutes later at 9.70 minutes, indicating effective resolution between the two compounds. The sharp and well-defined peaks suggest that the method is suitable for simultaneous analysis, likely intended for quality control or validation of pharmaceutical formulations containing both analytes.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe developed HPLC method demonstrated effective separation and reliable quantification of epinephrine (Rt\u0026thinsp;=\u0026thinsp;2.94\u0026thinsp;\u0026plusmn;\u0026thinsp;0.013 min) and articaine (Rt\u0026thinsp;=\u0026thinsp;9.79\u0026thinsp;\u0026plusmn;\u0026thinsp;0.035 min), with a resolution of 6.84\u0026thinsp;\u0026plusmn;\u0026thinsp;0.04 and no interfering peaks, confirming its specificity. Both analytes showed good peak shapes (tailing factor\u0026thinsp;\u0026lt;\u0026thinsp;1.5) and high column efficiency, with theoretical plates exceeding 5800. The method exhibited excellent linearity over a concentration range of 0.5\u0026ndash;20 \u0026micro;g/mL (r\u0026sup2; \u0026ge; 0.997), and low LOD and LOQ values (125 ng/mL and 250 ng/mL, respectively) for both the analytes. The accuracy was within acceptable limits, with recoveries ranging from 95.55\u0026ndash;100.89%, and precision was confirmed by low %CVs in both the repeatability and interday presion studies. Stability testing indicated minimal degradation under bench-top and autosampler conditions, supporting the robustness of the method. Validation data of the optimized analytical method for articaine and epinephrine are given in Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eValidation data of the optimized analytical method for articaine and epinephrine\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"3\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eParameters\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eEpinephrine\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eArticaine\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eRetention time (min)\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e2.94\u0026thinsp;\u0026plusmn;\u0026thinsp;0.013\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e9.79\u0026thinsp;\u0026plusmn;\u0026thinsp;0.035\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eTailing factor\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1.25\u0026thinsp;\u0026plusmn;\u0026thinsp;0.01\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e1.31\u0026thinsp;\u0026plusmn;\u0026thinsp;0.01\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eTheoretical plate\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e5858.92\u0026thinsp;\u0026plusmn;\u0026thinsp;34.22\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e8153.16\u0026thinsp;\u0026plusmn;\u0026thinsp;123.96\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eSpecificity\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e\u003cp\u003eNo interfering peaks at the tR of epinephrine and articaine\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eResolution\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e\u003cp\u003e6.84\u0026thinsp;\u0026plusmn;\u0026thinsp;0.04\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eLinearity range (\u0026micro;g/mL)\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.5\u0026ndash;20\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.5\u0026ndash;20\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eRegression equation\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003ey\u0026thinsp;=\u0026thinsp;4667.9x \u0026minus;\u0026thinsp;2357\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003ey\u0026thinsp;=\u0026thinsp;18441x \u0026minus;\u0026thinsp;1477.4\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eCorrelation coefficient (r\u003c/b\u003e\u003csup\u003e\u003cb\u003e2\u003c/b\u003e\u003c/sup\u003e\u003cb\u003e)\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.997\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.999\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eLOD (ng/mL)\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e125\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e125\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eLOQ (ng/mL)\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e250\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e250\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"3\" nameend=\"c3\" namest=\"c1\"\u003e\u003cp\u003e\u003cb\u003eAccuracy (% Recovery)\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e80%\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e96.09\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e99.05\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e100%\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e97.69\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e100.89\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e120%\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e95.55\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e98.85\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"3\" nameend=\"c3\" namest=\"c1\"\u003e\u003cp\u003e\u003cb\u003ePrecision (% CV)\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eRepeatability\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.81\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.15\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eInterday\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1.39\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.13\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"3\" nameend=\"c3\" namest=\"c1\"\u003e\u003cp\u003e\u003cb\u003eStability (% change)\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eBench-top\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e-1.21%\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.45\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eAutosampler\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e-0.91%\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e1.34\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\n\u003ch3\u003e4B. Physical compatibility:\u003c/h3\u003e\n\u003cp\u003eAll the test samples remained colorless and clear when observed against a white background. No samples presented any particulate matter or suspension when viewed against a black background.\u003c/p\u003e\u003cp\u003eThe pH significantly increased from baseline at both 8\u0026deg;C and 25\u0026deg;C (Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e) every hour until 8 hours but remained within the acceptable physiologic pH range of 7.35\u0026ndash;7.45 [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. There was no statistically significant difference between the increases in pH compared with the baseline at 8\u0026deg;C and 25\u0026deg;C at any time interval until 8 hours (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). The only exception was at 2 hours, where the difference was significant (\u003cem\u003ep\u0026thinsp;=\u0026thinsp;.018).\u003c/em\u003e\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab4\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eComparison of pH values between the baseline and each hour at 8\u0026deg;C and 25\u0026deg;C\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"6\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTime Interval\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003en\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eMean pH\u0026thinsp;\u0026plusmn;\u0026thinsp;SD\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eMean Difference\u0026thinsp;\u0026plusmn;\u0026thinsp;SD\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003et value\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003ep value\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003ctr\u003e\u003cth align=\"left\" colspan=\"6\" nameend=\"c6\" namest=\"c1\"\u003e\u003cp\u003e8 degrees\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eBaseline\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e7.05\u0026thinsp;\u0026plusmn;\u0026thinsp;0.05\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u0026ndash;\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u0026ndash;\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e\u0026ndash;\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e1 hour\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e7.12\u0026thinsp;\u0026plusmn;\u0026thinsp;0.08\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-0.07\u0026thinsp;\u0026plusmn;\u0026thinsp;0.03\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-4.04\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.056\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e2 hours\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e7.17\u0026thinsp;\u0026plusmn;\u0026thinsp;0.04\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-0.12\u0026thinsp;\u0026plusmn;\u0026thinsp;0.02\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-10.26\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.009\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e3 hours\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e7.19\u0026thinsp;\u0026plusmn;\u0026thinsp;0.06\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-0.14\u0026thinsp;\u0026plusmn;\u0026thinsp;0.01\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-24.25\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.002\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e4 hours\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e7.27\u0026thinsp;\u0026plusmn;\u0026thinsp;0.06\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-0.22\u0026thinsp;\u0026plusmn;\u0026thinsp;0.01\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-38.11\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.001\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e5 hours\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e7.38\u0026thinsp;\u0026plusmn;\u0026thinsp;0.03\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-0.33\u0026thinsp;\u0026plusmn;\u0026thinsp;0.02\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-28.58\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.001\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e6 hours\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e7.41\u0026thinsp;\u0026plusmn;\u0026thinsp;0.05\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-0.36*\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u0026ndash;\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e\u0026ndash;\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e7 hours\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e7.43\u0026thinsp;\u0026plusmn;\u0026thinsp;0.07\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-0.38\u0026thinsp;\u0026plusmn;\u0026thinsp;0.02\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-32.91\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.001\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e8 hours\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e7.45\u0026thinsp;\u0026plusmn;\u0026thinsp;0.08\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-0.40\u0026thinsp;\u0026plusmn;\u0026thinsp;0.03\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-23.09\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.002\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"6\" nameend=\"c6\" namest=\"c1\"\u003e\u003cp\u003e\u003cb\u003e25 degrees\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eBaseline\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e7.06\u0026thinsp;\u0026plusmn;\u0026thinsp;0.05\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u0026ndash;\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u0026ndash;\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e\u0026ndash;\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e1 hour\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e7.20\u0026thinsp;\u0026plusmn;\u0026thinsp;0.02\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-0.14\u0026thinsp;\u0026plusmn;\u0026thinsp;0.05\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-4.80\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.041\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e2 hours\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e7.26\u0026thinsp;\u0026plusmn;\u0026thinsp;0.02\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-0.20\u0026thinsp;\u0026plusmn;\u0026thinsp;0.03\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-12.20\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.007\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e3 hours\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e7.29\u0026thinsp;\u0026plusmn;\u0026thinsp;0.02\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-0.23\u0026thinsp;\u0026plusmn;\u0026thinsp;0.04\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-9.71\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.010\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e4 hours\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e7.32\u0026thinsp;\u0026plusmn;\u0026thinsp;0.01\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-0.26\u0026thinsp;\u0026plusmn;\u0026thinsp;0.04\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-12.05\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.007\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e5 hours\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e7.33\u0026thinsp;\u0026plusmn;\u0026thinsp;0.02\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-0.27\u0026thinsp;\u0026plusmn;\u0026thinsp;0.04\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-12.51\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.006\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e6 hours\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e7.38\u0026thinsp;\u0026plusmn;\u0026thinsp;0.01\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-0.32\u0026thinsp;\u0026plusmn;\u0026thinsp;0.04\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-12.72\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.006\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e7 hours\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e7.41\u0026thinsp;\u0026plusmn;\u0026thinsp;0.02\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-0.35\u0026thinsp;\u0026plusmn;\u0026thinsp;0.04\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-14.86\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.004\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e8 hours\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e7.42\u0026thinsp;\u0026plusmn;\u0026thinsp;0.02\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-0.36\u0026thinsp;\u0026plusmn;\u0026thinsp;0.03\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-21.80\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.002\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"6\" nameend=\"c6\" namest=\"c1\"\u003e\u003cp\u003e* t value cannot be calculated due to the same standard deviation in both the baseline and 6 hour values\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\n\u003ch3\u003e4C. Chemical Stability:\u003c/h3\u003e\n\u003cp\u003eThere was no significant degradation in the concentration of buffered articaine after 8 hours at either 8\u0026deg;C or 25\u0026deg;C (Table\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e5\u003c/span\u003e). There was also no significant difference when the degradation at 25\u0026deg;C and 8\u0026deg;C was compared (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e) at each sampling hour from the baseline. Therefore, articaine remained chemically stable at both 25\u0026deg;C and 8\u0026deg;C for 8 hours. However, the concentration of epinephrine significantly decreased at every test interval after 1 hour at 25\u0026deg;C (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.002) (Table\u0026nbsp;\u003cspan refid=\"Tab6\" class=\"InternalRef\"\u003e6\u003c/span\u003e) and after 2 hours at 8\u0026deg;C (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.038) (Table\u0026nbsp;\u003cspan refid=\"Tab6\" class=\"InternalRef\"\u003e6\u003c/span\u003e).\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab5\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 5\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eConcentrations of articaine at each sampling hour compared with the baseline at 8\u0026deg;C and 25\u0026deg;C\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"6\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTime Interval\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003en\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eMean % assay \u0026plusmn; SD\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eMean Difference\u0026thinsp;\u0026plusmn;\u0026thinsp;SD\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003et value\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003ep value\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003ctr\u003e\u003cth align=\"left\" colspan=\"6\" nameend=\"c6\" namest=\"c1\"\u003e\u003cp\u003e8 degrees\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eBaseline\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e95.78\u0026thinsp;\u0026plusmn;\u0026thinsp;1.15\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u0026ndash;\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u0026ndash;\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e\u0026ndash;\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e1 hour\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e95.64\u0026thinsp;\u0026plusmn;\u0026thinsp;1.00\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.14\u0026thinsp;\u0026plusmn;\u0026thinsp;0.18\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e1.36\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.306\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e2 hours\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e95.41\u0026thinsp;\u0026plusmn;\u0026thinsp;1.01\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.36\u0026thinsp;\u0026plusmn;\u0026thinsp;0.19\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e3.27\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.082\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e3 hours\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e95.02\u0026thinsp;\u0026plusmn;\u0026thinsp;1.37\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.76\u0026thinsp;\u0026plusmn;\u0026thinsp;0.47\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e2.80\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.107\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e4 hours\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e94.46\u0026thinsp;\u0026plusmn;\u0026thinsp;1.55\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.32\u0026thinsp;\u0026plusmn;\u0026thinsp;0.59\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e3.89\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.060\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e5 hours\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e93.30\u0026thinsp;\u0026plusmn;\u0026thinsp;0.28\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e2.48\u0026thinsp;\u0026plusmn;\u0026thinsp;1.41\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e3.05\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.093\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e6 hours\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e93.06\u0026thinsp;\u0026plusmn;\u0026thinsp;0.37\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e2.72\u0026thinsp;\u0026plusmn;\u0026thinsp;1.52\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e3.10\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.090\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e7 hours\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e92.84\u0026thinsp;\u0026plusmn;\u0026thinsp;0.36\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e2.93\u0026thinsp;\u0026plusmn;\u0026thinsp;1.50\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e3.39\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.077\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e8 hours\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e92.61\u0026thinsp;\u0026plusmn;\u0026thinsp;0.53\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e3.16\u0026thinsp;\u0026plusmn;\u0026thinsp;1.52\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e3.60\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.069\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"6\" nameend=\"c6\" namest=\"c1\"\u003e\u003cp\u003e\u003cb\u003e25 degrees\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eBaseline\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e94.95\u0026thinsp;\u0026plusmn;\u0026thinsp;0.54\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u0026ndash;\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u0026ndash;\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e\u0026ndash;\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e1 hour\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e94.11\u0026thinsp;\u0026plusmn;\u0026thinsp;1.11\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.84\u0026thinsp;\u0026plusmn;\u0026thinsp;1.04\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e1.40\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.297\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e2 hours\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e93.85\u0026thinsp;\u0026plusmn;\u0026thinsp;1.18\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.10\u0026thinsp;\u0026plusmn;\u0026thinsp;1.09\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e1.76\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.221\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e3 hours\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e93.77\u0026thinsp;\u0026plusmn;\u0026thinsp;1.15\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.19\u0026thinsp;\u0026plusmn;\u0026thinsp;1.09\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e1.89\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.200\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e4 hours\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e93.72\u0026thinsp;\u0026plusmn;\u0026thinsp;1.17\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.23\u0026thinsp;\u0026plusmn;\u0026thinsp;1.11\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e1.92\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.195\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e5 hours\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e93.52\u0026thinsp;\u0026plusmn;\u0026thinsp;1.21\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.43\u0026thinsp;\u0026plusmn;\u0026thinsp;1.07\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e2.32\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.146\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e6 hours\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e93.44\u0026thinsp;\u0026plusmn;\u0026thinsp;1.27\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.51\u0026thinsp;\u0026plusmn;\u0026thinsp;1.13\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e2.32\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.146\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e7 hours\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e93.24\u0026thinsp;\u0026plusmn;\u0026thinsp;1.25\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.71\u0026thinsp;\u0026plusmn;\u0026thinsp;1.01\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e2.92\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.100\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e8 hours\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e93.19\u0026thinsp;\u0026plusmn;\u0026thinsp;1.20\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.76\u0026thinsp;\u0026plusmn;\u0026thinsp;0.97\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e3.14\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.088\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"6\" nameend=\"c6\" namest=\"c1\"\u003e\u003cp\u003e* t value cannot be calculated due to the same standard deviation in both the baseline and 6 hour values\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab6\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 6\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eConcentration of epinephrine at each sampling hour compared with that at baseline at 8\u0026deg;C and 25\u0026deg;C\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"6\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTime Interval\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003en\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eMean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eMean Difference\u0026thinsp;\u0026plusmn;\u0026thinsp;SD\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003et value\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003ep value\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003ctr\u003e\u003cth align=\"left\" colspan=\"6\" nameend=\"c6\" namest=\"c1\"\u003e\u003cp\u003e8 degree\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eBaseline\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e98.63\u0026thinsp;\u0026plusmn;\u0026thinsp;1.34\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u0026ndash;\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u0026ndash;\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e\u0026ndash;\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e1 hour\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e97.30\u0026thinsp;\u0026plusmn;\u0026thinsp;0.77\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.33\u0026thinsp;\u0026plusmn;\u0026thinsp;0.65\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e3.52\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.072\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e2 hours\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e96.31\u0026thinsp;\u0026plusmn;\u0026thinsp;0.84\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e2.32\u0026thinsp;\u0026plusmn;\u0026thinsp;1.36\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e2.95\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.098\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e3 hours\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e95.78\u0026thinsp;\u0026plusmn;\u0026thinsp;0.81\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e2.85\u0026thinsp;\u0026plusmn;\u0026thinsp;1.00\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e4.95\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.038\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e4 hours\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e95.40\u0026thinsp;\u0026plusmn;\u0026thinsp;0.62\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e3.22\u0026thinsp;\u0026plusmn;\u0026thinsp;0.75\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e7.41\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.018\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e5 hours\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e94.89\u0026thinsp;\u0026plusmn;\u0026thinsp;0.95\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e3.74\u0026thinsp;\u0026plusmn;\u0026thinsp;0.70\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e9.26\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.011\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e6 hours\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e94.37\u0026thinsp;\u0026plusmn;\u0026thinsp;1.18\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e4.26\u0026thinsp;\u0026plusmn;\u0026thinsp;1.09\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e6.78\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.021\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e7 hours\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e94.01\u0026thinsp;\u0026plusmn;\u0026thinsp;1.24\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e4.62\u0026thinsp;\u0026plusmn;\u0026thinsp;1.28\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e6.26\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.025\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e8 hours\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e93.63\u0026thinsp;\u0026plusmn;\u0026thinsp;1.29\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e5.00\u0026thinsp;\u0026plusmn;\u0026thinsp;1.51\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e5.75\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.029\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"6\" nameend=\"c6\" namest=\"c1\"\u003e\u003cp\u003e\u003cb\u003e25 degree\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eBaseline\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e97.62\u0026thinsp;\u0026plusmn;\u0026thinsp;0.38\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u0026ndash;\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u0026ndash;\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e\u0026ndash;\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e1 hour\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e97.38\u0026thinsp;\u0026plusmn;\u0026thinsp;0.57\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.23\u0026thinsp;\u0026plusmn;\u0026thinsp;0.19\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e2.06\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.176\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e2 hours\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e97.19\u0026thinsp;\u0026plusmn;\u0026thinsp;0.40\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.42\u0026thinsp;\u0026plusmn;\u0026thinsp;0.03\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e23.67\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.002\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e3 hours\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e96.63\u0026thinsp;\u0026plusmn;\u0026thinsp;0.30\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.99\u0026thinsp;\u0026plusmn;\u0026thinsp;0.43\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e4.01\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.057\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e4 hours\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e96.27\u0026thinsp;\u0026plusmn;\u0026thinsp;0.19\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.35\u0026thinsp;\u0026plusmn;\u0026thinsp;0.52\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e4.51\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.046\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e5 hours\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e96.04\u0026thinsp;\u0026plusmn;\u0026thinsp;0.22\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.57\u0026thinsp;\u0026plusmn;\u0026thinsp;0.60\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e4.56\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.045\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e6 hours\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e95.59\u0026thinsp;\u0026plusmn;\u0026thinsp;0.41\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e2.03\u0026thinsp;\u0026plusmn;\u0026thinsp;0.79\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e4.46\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.047\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e7 hours\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e95.19\u0026thinsp;\u0026plusmn;\u0026thinsp;0.42\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e2.43\u0026thinsp;\u0026plusmn;\u0026thinsp;0.79\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e5.32\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.034\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e8 hours\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e94.29\u0026thinsp;\u0026plusmn;\u0026thinsp;0.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e3.33\u0026thinsp;\u0026plusmn;\u0026thinsp;0.88\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e6.55\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.022\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"6\" nameend=\"c6\" namest=\"c1\"\u003e\u003cp\u003e* t value cannot be calculated due to the same standard deviation in both the baseline and 6 hour values\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eBuffering or, more appropriately, alkalinization is the process of adding a basic solution to an acidic solution such as a commercially available local anesthetic solution [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. This study examined the physical and chemical stability of a 4% buffered articaine solution with 1:100,000 epinephrine. We studied the stability of epinephrine along with 4% articaine because epinephrine is an integral part of any local anesthetic solution and has numerous clinical advantages [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. The solutions were evaluated for 8 hours to complement the average duration of clinical functioning. The solutions were tested at two temperatures, 25\u0026deg;C and 8\u0026deg;C, to provide recommendations on the mode of storage of the buffered articaine solution. A 10:1 dilution with 8.4% sodium bicarbonate was used to assess physical stability. The amount of basic solution must be specified because an excess amount will cloud and precipitate the local anesthetic solution [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. A validated HPLC method was used for the study of chemical stability [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eThe articaine samples containing epinephrine were physically stable throughout the test period at both temperatures. They remained clear, colorless and devoid of particulate matter on examination. There were also no significant changes in pH. Similar results have been published with respect to the physical stability of lidocaine by various authors [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. This study provides similar data for articaine.\u003c/p\u003e\u003cp\u003eAll the buffered articaine samples retained at least 92.61% and 93.19% of the original concentration at 8\u0026deg;C and 25\u0026deg;C, respectively. We measured the concentrations only for 8 hours, unlike previous studies that measured the stability of lidocaine for periods of up to 7 days [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. We rationalized that preparing fresh solutions at the beginning of each working day is feasible in any practice. This is especially important until we obtain more long-term data on buffered articaine solutions.\u003c/p\u003e\u003cp\u003eEpinephrine significantly decreased in concentration, i.e., 93.63% and 94.28% of the initial concentration at both 8\u0026deg;C and 25\u0026deg;C, respectively, at 8 hours. Epinephrine 4-[1R)-1-(3,4-dihydroxyphenyl)-2-(methylamino) ethanol] is an injectable solution that contains catecholamines. These catecholamine-containing injectable solutions are unstable under alkaline environments and at high temperatures, primarily because the oxidation of catecholamines promotes their breakdown [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. The nature and effect of the degradation products of epinephrine-containing articaine injectables require further research.\u003c/p\u003e\u003cp\u003eThe limitation of this study is that these results cannot be extrapolated to assign expiration dates to buffered articaine solutions with epinephrine in actual clinical settings. This study addresses only one aspect of buffered articaine, namely, its shelf life, and does not address its clinical effectiveness. Future studies should focus on the clinical efficacy of buffered articaine with epinephrine stored for various time intervals at varying temperatures.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eUnder the conditions of the study, we can draw the following conclusions:\u003c/p\u003e\u003cp\u003e\u003cul\u003e\u003cli\u003e\u003cp\u003eFour percent articaine with 1:100,000 epinephrine remained physically stable for 8 hours at 8\u0026deg;C and 25\u0026deg;C.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eFour percent articaine remained chemically stable in terms of concentration at both 25\u0026deg;C and 8\u0026deg;C for 8 hours.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eEpinephrine significantly decreased in concentration at every test interval after 1 hour at 25\u0026deg;C and after 2 hours at 8\u0026deg;C.\u003c/p\u003e\u003c/li\u003e\u003c/ul\u003e\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eConflict of interest:\u003c/strong\u003e Nil\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements:\u003c/strong\u003e Nil\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData Availability statement:\u003c/strong\u003e The original data is available with the corresponding author and can be shared on request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics:\u003c/strong\u003e Institutional Ethics Committee approval was obtained from Manipal College of Dental Sciences, Mangalore (Protocol reference number: 22089).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eSource of Funding:\u003c/strong\u003e The authors received no specific funding for this work.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors' contributions:\u003c/strong\u003e SP, SM, AG and AR were responsible for the concept, data acquisition, drafting the article, revision and final approval. SN was involved in data analysis and interpretation, and final approval of the manuscript. KYM and AN were involved in revision and final approval of the manuscript.\u0026nbsp;\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eOgle OE, Mahjoubi G. Advances in local anesthesia in dentistry. Dental Clinics. 2011;55(3):481\u0026ndash;99.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eSaxena P, Gupta SK, Newaskar V, Chandra A. Advances in dental local anesthesia techniques and devices: An update. National journal of maxillofacial surgery. 2013;4(1):19.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eBassett KB, DiMarco AC, Naughton DK. Dental local anesthetic drugs, articaine. In: \u003cem\u003eLocal Anesthesia for Dental Professionals\u003c/em\u003e. 2nd ed. Upper Saddle River, NJ: Pearson Education; 2015: 55\u0026ndash;58.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eMalamed SF, Tavana S, Falkel M. Faster onset and more comfortable injection with alkalinized 2% lidocaine with epinephrine 1: 100,000. Compend Contin Educ Dent. 2013;34(1):10\u0026ndash;20.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eJorgenson K, Burbridge L, Cole B. Comparison of the efficacy of a standard inferior alveolar nerve block versus articaine infiltration for invasive dental treatment in permanent mandibular molars in children: a pilot study. European Archives of Pediatric Dentistry. 2020;21(1):171\u0026ndash;7.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eAnesthetic efficacy of buffered 4% articaine for mandibular first molar infiltration: a crossover clinical trial. J Dent Anesth Pain Med. 2023;23(3):135\u0026ndash;141. doi: \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.17245/jdapm.2023.23.3.135\u003c/span\u003e\u003cspan address=\"10.17245/jdapm.2023.23.3.135\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eLi J, Brainard D. Premixed buffered lidocaine retains efficacy after prolonged room temperature storage. Am J Emerg Med. 2000; 18(2): 235\u0026ndash;236.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eShurtz R, Nusstein J, Reader A, Drum M, Fowler S, Beck M. Buffered 4% articaine as a primary buccal infiltration of the mandibular first molar: A prospective, randomized, double-blind study. Journal of endodontics. 2015;41(9):1403\u0026ndash;7.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eStewart JH, Cole GW, Klein JA. Neutralized lidocaine with epinephrine for local anesthesia. J Dermatol Surg Oncol 3. Mollica JA, Ahuja S, Cohen J. Stability of pharmaceuticals. J 1989;15:1081-3\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eLarson PO, RAGI G, Swandby M, Darcey B, Polzin G, Carey P. Stability of buffered lidocaine and epinephrine used for local anesthesia. The Journal of dermatologic surgery and oncology. 1991;17(5):411\u0026ndash;4.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eGuideline IH. Analytical procedure development Q14. International Council for Harmonization of Technical Requirements for Pharmaceuticals for Human Use: Geneva, Switzerland. 2022 Mar 24.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eHopkins E, Sanvictores T, Sharma S. Physiology, Acid Base Balance. 2022 Sep 12. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan\u0026ndash;.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eBrandis K. Alkalinization of local anesthetic solutions. Aust Prescr 2011;34:173\u0026ndash;5\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eTschopp C, Tram\u0026egrave;r MR, Schneider A, Zaarour M, Elia N. Benefit and Harm of Adding Epinephrine to a Local Anesthetic for Neuraxial and Locoregional Anesthesia: A Meta-analysis of Randomized Controlled Trials With Trial Sequential Analyses. Anesth Analg. 2018;127(1):228\u0026ndash;239.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003ePascuet E, Donnelly RF, Garceau D, Vaillancourt R. Buffered lidocaine hydrochloride solution with and without epinephrine: stability in polypropylene syringes. The Canadian journal of hospital pharmacy. 2009;62(5):375.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eDonnelly RF. Stability of buffered lidocaine in glass vials. The Canadian Journal of Hospital Pharmacy. 2011;64(4):289.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eHoellein L, Holzgrabe U. Ficts and facts of epinephrine and norepinephrine stability in injectable solutions. Int J Pharm. 2012;434(1\u0026ndash;2):468\u0026ndash;80.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"articaine, sodium bicarbonate, buffering, alkalinization","lastPublishedDoi":"10.21203/rs.3.rs-7195283/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7195283/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003eObjective: \u003c/strong\u003eThere is a lack of scientific data on the shelf-life of buffered articaine solutions. This study evaluated the physical and chemical stability of buffered 4% articaine with 1:100,000 epinephrine.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMaterials and Methods:\u003c/strong\u003e For the study of physical stability, two groups (1P, 2P) \u003cem\u003e(“P” designating samples to study physical stability)\u003c/em\u003e of triplet samples were prepared. The 1P samples were stored at 8 °C, and the 2P samples were stored at 25°C. The samples were evaluated every hour till 8 hours by inspecting the appearance of particulate matter against a black background, color change against a white background and pH using a calibrated pH meter. For the study of chemical stability, 4 groups (1C, 2C, 3C and 4C) \u003cem\u003e(“C” designating samples to study chemical stability\u003c/em\u003e) of triplet samples were prepared. 1C and 2C were used to evaluate the stability of articaine stored at 8°C and 25°C. 3C and 4C were used to evaluate the stability of epinephrine stored at 8°C and 25°C,respectively. The samples were evaluated every hour till 8 hours using a validated high-performance liquid chromatography method. Independent tests were applied for statistical analysis.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResults\u003c/strong\u003e: All the test samples remained colorless and clear for a period of 8 hours. The pH significantly increased from baseline at both 8°C and 25°C every hour until8 hours but remained within the acceptable physiological pH. There was no significant degradation in the concentration of buffered articaineafter 8 hours at either 25°C or 8°C. However, the concentration of epinephrine significantly decreased at every test interval after 1 hour at 25°C (\u003cem\u003ep\u003c/em\u003e = 0.002)and after 2 hours at 8°C (\u003cem\u003ep\u003c/em\u003e= 0.038).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConclusion\u003c/strong\u003e: The buffered articaine solution remained physically stable at 8 hours. The buffered articaine solution remained chemically stable at 8 hours at 8°C and 25°C. Epinephrine remained chemically stable for 2 hours at 8°C and 1 hour at 25°C.\u003c/p\u003e","manuscriptTitle":"Physical and Chemical Stability of Buffered Articaine: An In-Vitro Study","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-07-31 10:16:11","doi":"10.21203/rs.3.rs-7195283/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"2cb31d7d-84c5-45f3-8c3e-8ec5cf62edee","owner":[],"postedDate":"July 31st, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":52283939,"name":"Health sciences/Health care/Dentistry/Dental treatments"},{"id":52283940,"name":"Health sciences/Health care/Dentistry"}],"tags":[],"updatedAt":"2025-11-07T18:31:00+00:00","versionOfRecord":[],"versionCreatedAt":"2025-07-31 10:16:11","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7195283","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7195283","identity":"rs-7195283","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}