Effect of Ophthalmic Preparation of Methyldopa on Induced Ocular Hypertension in rabbits

Effect of Ophthalmic Preparation of Methyldopa on Induced Ocular Hypertension in rabbits | 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 Research Article Effect of Ophthalmic Preparation of Methyldopa on Induced Ocular Hypertension in rabbits Foouad Kadhim Gatea, Zeena Ayad Hussein, Haitham Kadhim Mahmood, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-5234809/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 30 Oct, 2024 Read the published version in Naunyn-Schmiedeberg's Archives of Pharmacology → Version 1 posted 7 You are reading this latest preprint version Abstract Glaucoma is a type of ocular disorder with multifaceted etiologies characterized by progressive optic nerve damage and ultimately loss of visual field. This study evaluated the possible IOP-lowering effect of an ophthalmic preparation of methyldopa in corticosteroid-induced ocular hypertension in rabbits. 40 New Zealand white male rabbits were assigned to the experiment and then randomly divided into 5 groups (n = 8). Ocular hypertension was induced by weekly subconjunctival injection of betamethasone suspension in both eyes. Animal groups included the control (healthy) group, which received the ophthalmic vehicle only, the standard (timolol) group, which received 0.5% timolol ED, and the MD groups, which received 0.5%, 1%, and 2% of methyldopa ophthalmic preparation. Treatments were applied to the right eye twice daily for 7 days whereas the left eye served as control and was given only distilled water. IOP was recorded and ocular reflexes were observed. Weekly subconjunctival injections of betamethasone resulted in a significant elevation in the IOP (P ≤ 0.001) that was reduced after treatments with timolol 0.5% and MD at different concentrations. Timolol showed the highest reduction (P ≤ 0.001) in the mean IOP with a 30% reduction. MD showed a concentration-dependent reduction with the highest reduction (P ≤ 0.01) observed at 2% compared to the induced/DW eyes and no significant difference compared to the timolol 0.5% (P ≥ 0.05) with a 24.2% reduction in the mean IOP. Methyldopa managed to reduce the IOP in the chronic model of glaucoma, making MD a promising addition to the anti-glaucoma medications. Glaucoma Corticosteroids Methyldopa Timolol Intraocular pressure Rabbits Figures Figure 1 Figure 2 Figure 3 Figure 4 Introduction Glaucoma is an eye disease characterized by progressive damage to the optic nerve and loss of retinal ganglion cells (RGCs) (Azuara-Blanco et al. 2020 ). Eventually, this leads to blindness. A person with glaucoma can have either a primary or secondary cause. In primary open-angle glaucoma, nerve fibers in the retina and the optic nerve edge are lost, resulting in visual field defects. Risk factors for IOP elevation include elevated intraocular pressure (IOP) and advanced age (Leung and Tham 2022 ). In normal-tension glaucoma (NTG), damage to the optic nerve and loss of RGCs occurs even if the intraocular pressure remains within the normal range (Trivli et al. 2019 ). Secondary glaucoma conditions are caused by another ocular disease or health problem, such as injury, inflammation, or certain medications (Tsai et al. 2024 ). The exact pathogenesis of the disease is still unknown. Excitotoxicity is thought to involve immunological mechanisms (Bell et al. 2018 ), such as microglial inflammatory responses (Karlstetter et al. 2015 ), ischemic processes (Guan et al., 2020 ), and oxidative stress (Shu et al. 2023 ). Elevated intraocular pressure (IOP) is considered the most common risk factor for the development and progression of glaucoma. It is an important pathophysiological factor for neurodegeneration and optic nerve damage (Amato 2022 ). Although Mendelian inheritance occurs in a normal adult-onset form, heredity may play a role in Mendelian inheritance as the primary mode of inheritance (Khaled Alsirhani et al., 2020 ). Lowering intraocular pressure is thought to help slow glaucoma damage to the optic nerve and visual field (Leske et al. 2003 ). Lowering intraocular pressure has proven to be the only proven way to treat the disease effectively. Glaucoma medications, usually in the form of eye drops, are often the first treatment option as they reduce aqueous humor production or improve drainage (Cordeiro et al. 2023 ). Other approaches, such as laser therapy and surgery, may also be options. The prevalence of glaucoma is significantly higher in older adults, especially those over 40 years of age, compared to younger people (Khaled Alsirhani et al. 2020 ). It is known that corticosteroids can cause ocular hypertension (OH) regardless of the route of administration (Phulke et al. 2017 ). Significant increases in intraocular pressure can occur within hours or a few days after taking steroids. IOP usually normalizes once the medication is discontinued; however, this side effect may be irreversible in certain individuals (Overby and Clark 2015 ). The precise mechanism by which corticosteroids increase intraocular pressure has yet to be elucidated. However, it is known that steroids cause stabilization of lysosomal membranes and accumulation of polymerized glycosaminoglycans within the trabecular meshwork (TM), creating a significant resistance to aqueous humor (AH) outflow. Furthermore, these agents also enhance TM resistance by increasing the expression of fibronectin, elastin, and laminin (Nuyen et al. 2017 ). Methyldopa (MD) exerts its antihypertensive effect through a central mechanism involving biotransformation to methyl-norepinephrine (Seremak-Mrozikiewicz and Drews 2004 ). Methyldopa is taken up by adrenergic neurons, where it is decarboxylated and hydroxylated to form the pseudo-neurotransmitter, methyl-noradrenaline, which has lower activity at α-receptors than norepinephrine and is, therefore, less effective at causing vasoconstriction (Noei et al. 2017 ). α-Methyldopa has central and peripheral mechanisms of action. Only the L-isomer of α-methyldopa can inhibit dopa decarboxylase and remove norepinephrine from animal tissues. Methyldopa is reliably absorbed from the gastrointestinal tract and easily enters the central nervous system. It has a half-life of 1.5 hours (Peter 2012). Due to its safety profile for the fetus, it is considered the first-line antihypertensive drug for the treatment of preeclampsia during pregnancy. The most commonly associated side effects include sedation, nightmares, sexual dysfunction, and depression (Peter 2012; Bogacz et al. 2021 ). This study evaluated the possible IOP-lowering effect of an ophthalmic preparation of methyldopa in corticosteroid-induced ocular hypertension in rabbits. Materials & Methods Chemicals and Reagents: Chemicals and drugs used in the study were purchased from different sources; methyldopa and benzalkonium chloride powders were purchased from (HyperChem, Hangzhou, China), betamethasone suspension ampule (Celestone® Chronodose®) containing betamethasone acetate 3mg and betamethasone sodium phosphate 3.9mg manufactured by (Schering Plough, Belgium), Xylazine HCl (XYL-M2, VMD ® Livestock Pharma, Belgium). Ketamine HCl (Ketamine 10%, Alfasan Nederland BV, Holand). Tetracaine HCl 0.5% w/v eye drops (Alcon, USA). Tobramycin 0.3% w/v eye drops (Tobrex®, Alcon, USA). Timolol 0.5% w/v eye drops (Lithimole®, COOPER Pharmaceuticals, Greek). Preparation of Methyldopa Ophthalmic Drops: Two solutions of 1/15M phosphate buffer with a pH of 7.4 were mixed in certain proportions to produce a phosphate buffer solution at pH (7.4). The first solution was prepared by dissolving 9.64 grams of sodium hydrogen phosphate in one litter of double-distilled water (DDW). The second solution was prepared by dissolving 8 g of sodium dihydrogen phosphate in one liter of DDW. One liter of a phosphate buffer solution was prepared by mixing 800 ml of the first and 200 ml of the second. 0.45 g of NaCl was added to make each 100 ml of phosphate-buffered solution isotonic. An ophthalmic solution of methyldopa was prepared by dissolving the desired amount of the tested drug powder in an appropriate volume of phosphate buffer solution with sufficient NaCl to make the solution isotonic. The mixture was stirred well with an ultrasonic shaker to enhance the dissolution followed by adding benzalkonium chloride solution and completing the final volume with a phosphate-buffered solution. The solution pH was adjusted to (7.4) by adding a few drops of phosphoric acid or sodium hydroxide solution. The final solution was filtered using a 0.22µm filter syringe to ensure clarity and sterility and then filled in previously autoclaved dropper containers (Allen et al. 2005 ), (Hameed et al. 2020 ). The formula used for the preparation of methyldopa ophthalmic solution was adapted from the British pharmacopeia for the preparation of a standard 0.3% ophthalmic agent that requires 0.3g of the test agent, 1% (v/v) of benzalkonium chloride solution, 0.45g of sodium chloride, and 1ml of absolute ethanol. Experimental Animals & Housing: The study was conducted in the animal house of the College of Medicine / Al-Nahrain University. New Zealand albino male rabbits aged (5–6) months weighing 1.5–2 kg were purchased from the Al-Rhazi Center / Ministry of Industry and Minerals. Animals were housed in clean and sterile conditions with (23 + 2) °C temperature and humidity around 45%-, and a 12-hour light/night cycle and left to acclimatize to the new environment for one week with free access to water and food. Rabbits were kept in pairs per cage, cages were stainless steel, and provided enough clean substrate to permit the animal's natural behavior. The cages were cleansed and washed every other day throughout the entire experiment. Rabbits' diet consisted mostly of standard pelleted balanced nutrition along with hay. Fresh greens including lettuce, parsley, and carrots were added to the diet three times weekly. Study Design & Settings: The experimental procedures were carried out in the animal handling room of the Department of Pharmacology / College of Medicine / Al-Nahrain University. 40 New Zealand White male rabbits were included in the experiment. The animals were divided randomly into 5 groups (n = 8) applying a block randomization algorithm. In the control group; the animals received only isotonic buffer solution in the right eye and distilled water (DW) in the left eye without induction with betamethasone, the remaining 32 animals received a subconjunctival injection of betamethasone suspension (betamethasone acetate 3mg and betamethasone sodium phosphate 3.9mg) weekly over 21 days in both eyes to induce ocular hypertension. Animals were randomly assigned to the remaining treated groups; inclusion criteria were (animals with successful elevation in the IOP were included, whereas animals that failed to develop ocular hypertension or those showing signs of eye irritation and discharge were excluded and put in separate cages). Treatments were installed on day 24 of the induction. The remaining treated groups were; the timolol group (served as the standard treatment), in which animals received timolol 0.5% ED, the Methyldopa (MD) groups, which received different concentrations of MD ocular preparation (0.5%, 1%, and 2%) (Mori et al. 2024 ) respectively as illustrated in Figure (1). All treatments were given twice daily at 6-hour intervals (8:00 AM and 2:00 PM) in the right eye and DW in the left eye. Treatments were continued for 7 days, and all animals were subjected to the same handler throughout the experiment. Induction of Ocular Hypertension in Rabbits: The protocol for inducing ocular hypertension was based on the method developed by Melena et al, with some adjustments. Melena et al observed that this model of induction closely resembles chronic open-angle glaucoma in humans (Melena et al. 1998 ). Rabbits were anesthetized through injection in the marginal ear with (ketamine HCl 60mg/kg and xylazine HCl 10mg/kg, IV). Using a micro-fine syringe, the animals were given a subconjunctival injection of 0.7 ml of betamethasone suspension (Khan et al. 2014 ). IOP measurements were conducted twice weekly to prevent damage to the corneal epithelium from frequent tonometry. The initial measurement was taken just before the weekly betamethasone subconjunctival injection, and the second measurement was taken three days after the injection. The animals received weekly betamethasone subconjunctival injections for a total of 21 days. The administration of the tested drugs began on the 24th day of betamethasone injection (three days after the fourth subconjunctival injection). Measurement of Intraocular Pressure (IOP): Corneal local anesthesia was applied using 1–2 drops of tetracaine HCL ophthalmic solution. The animal was held and restrained using a towel wrapped securely around its body. A Schiotz tonometer (Sartorius, Germany) was placed on the cornea. The IOP was measured 1 hour following the application of each test drug and an average of three readings was recorded. Before and after each measurement, the instrument was properly sterilized with 70% alcohol. As a prophylactic measure to prevent any opportunistic microbial infection by the device or during drug administration, an ophthalmic eye drop preparation of tobramycin 0.3% w/v was instilled twice (one time before the application of the device and again at the end of the measurement) (Jasim et al. 2019 ). Determination of percentage of IOP reduction: To help quantify the effectiveness of the treatment in reducing IOP in experimental glaucoma models, the following formula was applied to calculate the percentage of reduction in the IOP in an experimental study (Mansberger et al. 2012 ): $$\:\%\:reduction=\frac{\text{b}\text{a}\text{s}\text{e}\text{l}\text{i}\text{n}\text{e}\:\text{I}\text{O}\text{P}-\text{p}\text{o}\text{s}\text{t}\:\text{t}\text{r}\text{e}\text{a}\text{t}\text{m}\text{e}\text{n}\text{t}\:\text{I}\text{O}\text{P}}{\text{b}\text{a}\text{s}\text{e}\text{l}\text{i}\text{n}\text{e}\:\text{I}\text{O}\text{P}}\:X\:100$$ Assessment of ocular reflexes: Pupil diameter changes were measured using the pupil gauge penlight (Adelite™, American Diagnostic, USA). The results were presented in a millimeter unit (Ahuja 2003 ), (Alwany et al. 2017 ). The most important corneal reflexes are light, corneal local anesthetic effect, and conjunctival redness and lacrimation. The light reflex or pupillary response for both eyes was tested by swinging a flashlight to detect a relative afferent papillary defect. The corneal local anesthetic effect was tested using a wisp of cotton wool from the side. Finally, the conjunctiva of both eyes was examined for any signs of redness, swelling, and lacrimation. The observations for corneal reflexes were recorded as absent or present (Alwany et al. 2017 ). Sample Size calculation: The sample size was determined utilizing the program G*Power for sample size calculation (Faul et al. 2007 ) based on Cohen’s principles (Charan and Kantharia 2013 ), post hoc analysis was used with an effect size of 0.5 and an alpha level of 0.05, F-family tests with a total ‎sample size of 40 and each group of 8 animals. Statistical Analysis: Data analysis was carried out utilizing GraphPad Prism 8.0. A paired t-test was used to compare the results before and after applying an agent in the right eye of a given group. A one-way analysis of variance (ANOVA), followed by a Tukey test comparison, was utilized to compare the groups. The level of significance was set at P < 0.05. Data are presented as mean ± SEM (standard error of the mean). Results Data analysis of the study revealed that the animals in the control group (normotensive) that received the non-medicated ocular preparation (vehicle) in the left eye didn’t exhibit any changes in the IOP and remained constant throughout the timeline of the treatment (7 days) and with normal ocular reflexes including (pupil diameter, no discharge or irritation, no lacrimation, active light reflex, and no local anesthetic effect) as demonstrated in figure (2A) and table (1). Animals in the remaining experimental groups that received weekly subconjunctival injections of betamethasone suspension in both eyes that were successfully included in the experiment managed to show a gradual elevation in the IOP by the end of the second week after the second injection with a peak elevation after the fourth injection resulting in an IOP as high as 24 mmHg which was statistically significant when compared to the control group (P ≤ 0.001) as shown in figure (2). Animals that received the standard treatment of IOP (timolol 0.5%, ED) twice daily for seven days showed a gradual reduction in the IOP compared to the left eye that received only distilled water. The IOP in the right eye of the rabbits before starting the treatment was recorded (23.9 ± 0.85 mmHg). Once treatment with timolol, 0.5% ED was initiated, a gradual reduction in the IOP was observed with a significant reduction (P ≤ 0.05) observed on day 4 of the treatment by 3.7 mmHg and a maximum reduction in the IOP by 7.1 mmHg seen at the end of the experiment (day 7) with marked significant difference when compared to the left eye (P ≤ 0.01) as shown in figure (2). Timolol 0.5% ED exhibited a percentage reduction in the IOP that reached 30% as shown in Figure (4B). Animals that received ophthalmic preparation of methyldopa with different concentrations (0.5%, 1%, and 2%) twice daily for seven days exhibited varying degrees of IOP reduction with percentages of 7.5, 18.3, and 24.2 respectively as shown in Figure (4B). The recorded IOP of the right eye treated with methyldopa groups before starting the treatment was (23.9 ± 0.17, 24.5 ± 0.49, and 24 ± 0.74) for the selected methyldopa concentrations. As the methyldopa application was initiated, the animal group that received 0.5% of the preparation showed a reduction in IOP by 0.7 mmHg on day 4 of the treatment that was of no statistical significance (P ≥ 0.05) when compared to the left eye and then a maximum reduction in the IOP by 1.7 mmHg by the end of the experiment (day 7) that showed statistical significance (P ≤ 0.05) compared to the left eye that received DW. On the other hand, animal groups that received 1% and 2% of MD preparation showed better outcomes, where there was a significant reduction in the IOP by (2.3 mmHg, P ≤ 0.05) and (3.1 mmHg, P ≤ 0.05) respectively on day 4 of the treatment with a maximum reduction in the IOP by (4.9 mmHg, P ≤ 0.01) and (5.8 mmHg, P ≤ 0.01) by the end of the experiment (day 7) when compared to the left eye that received DW as shown in figure (2B, 2C, and 2D). Compared to the results of the standard (timolol 0.5%) group, animals that received MD 0.5% showed a significant difference but in favor of timolol (P = 0.043), whereas the other groups that received MD 1% and 2% showed comparable outcomes to timolol with statistical significance of (P = 0.739 and P = 948) respectively as shown in figure (2C and 2D). MD showed a concentration-dependent reduction in the IOP among animal groups and the best outcome was observed in the animal group treated with MD 2% as observed in Figure (4A). Animal groups that received ophthalmic treatments with timolol 0.5% or MD didn’t show any changes in ocular reflexes, with pupil diameter remaining constant and unaffected among all animal groups [Figure (3)], an intact light reflex, an intact reflex to applying cotton wool (no local anesthetic effect), and no signs of irritation and lacrimation throughout the treatment timeline, as shown in Table (1). Table 1 Effect of the ocular agents on most important ocular reflexes Parameter Treatments Vehicle Timolol 0.5% MD 0.5% MD 1% MD 2% Lacrimation Absent Absent Absent Absent Absent Conjunctival redness Absent Absent Absent Absent Absent Local anesthetic effect Absent Absent Absent Absent Absent Light reflex Present Present Present Present Present MD = methyldopa. Results were observational and only presented as (present or absent) Discussion Glaucoma is the primary cause of irreversible blindness on a global scale (Sun et al. 2022 ). Glucocorticoids are commonly used to treat immune-related and inflammatory conditions, but their chronic use, regardless of the administration method, can lead to various side effects, including the development of ocular hypertension. If left untreated, glucocorticoid-induced ocular hypertension may progress to glucocorticoid-induced glaucoma, resulting in the loss of retinal ganglion cells (Harvey et al. 2024 ). The model of glucocorticoid-induced ocular hypertension in rabbits is widely used due to its simplicity in experimental development, easy maintenance, and cost-effectiveness, as highlighted by Evangelho et al. (2019). Glaucoma induced by corticosteroids in rabbits resembles primary open-angle glaucoma in humans (Werner et al. 2006 ) and provides valuable insights into certain aspects of glaucoma pathology, given its anatomical and aqueous humor dynamics similarities with the human eye, as demonstrated in studies by Abdulsahib et al. ( 2015 ), Evangelho et al. (2015), and Hameed et al. ( 2020 ), providing both morphological and molecular evidence of glaucoma's pathogenesis. The study showed that weekly subconjunctival administration of betamethasone resulted in mild elevation in the IOP within the first week of the administration with maximum and statistically significant elevation (P ≤ 0.001) seen after the fourth administration with IOP (24 ± 0.2) on day 24 of the experiment. These results were consistent with previous studies using a corticosteroid model for the induction of IOP (Khan et al. 2014 ; Hussein et al. 2017 ; Jasim et al. 2019 ; Abdulsahib and Abood 2021 ; Sharif et al. 2024 ). It was speculated that the glaucoma effect produced by the chronic administration of glucocorticoids resulted from TM stiffness that hindered the outflow of the AH. Glucocorticoids cause TM stiffness by increasing the expression of transforming growth factor-β2 which in turn increases the extracellular matrix synthesis and deposition by activating the Smad2/3 pathway and other pathways leading to increased formation of TM cross-linked actin networks (CLANs), decreased cellularity of TM, and finally increased resistance to AH outflow from the canal of Schlemm (Harvey et al. 2024 ; Sharif et al. 2024 ). Although the eye is known to tolerate preparations of different pH, MD's ophthalmic preparation was still buffered to a pH close to that of the normal lacrimal fluid to minimize ocular irritation and discomfort. The addition of benzalkonium chloride was to enhance the effectiveness of the drug substance administered to the eye by modifying the penetration barrier of the cornea and promoting the adhesion of eye drops to the cornea; furthermore, the benzalkonium chloride acts as a preservative (Allen et al. 2005 ). This was proven by the control group's results, in which the animals received the ophthalmic vehicle only in the left eye and didn’t exhibit any significant changes (P ≥ 0.05) in the IOP or ocular reflexes. The epithelium, muscle, and vasculature of the ciliary body (CB) all contain nerve terminals. Within the ciliary epithelium (CE), there are α2 and β2 adrenergic receptors. Therefore, reducing aqueous humor (AH) formation can be achieved by stimulating the α-receptors or inhibiting the β-adrenergic receptors (Prunte and Markstein 2000 ). When the β2-receptor in the ciliary body is stimulated, it leads to the stimulation of adenylyl cyclase, resulting in an increase in cyclic adenosine monophosphate (cAMP), which in turn increases AH production (Brain and Hoffman 2007). Timolol maleate 0.5% eye drops, a well-known non-selective β-adrenoceptor blocker approved as one of the treatment choices for mild to moderate open-angle glaucoma. Timolol was used as a standard (positive control) in this study to compare MD's effectiveness with, another adrenoceptor-acting agent, used as an ophthalmic preparation. The study showed that timolol 0.5% ED had a noticeable ocular hypotensive effect with a significant (P ≤ 0.01) reduction in the mean IOP after one day of its application. It exhibited a marked decrease in the mean IOP on day 7 of the treatment, in which the final IOP showed no significant difference when compared to that of the normal group (P ≥ 0.05). These results were greatly supported by a previous finding done by Lee et al, where the study used timolol 0.5% ED as a positive control in the rabbit model of ocular hypertension and the results revealed that timolol managed to markedly reduce the IOP within 1–2 hours post-application compared to the control (Lee et al. 2022 ). Finally, based on these results, timolol 0.5% ED produced a 30% reduction in the mean IOP as shown in Figure (4B). The results of this study were consistent with previous findings done by Gupta et al, where the outcome of the study showed that timolol 0.5% managed to reduce mean IOP by 20% − 35% in ocular hypertensive eyes (Gupta et al. 2007 ). The effects of timolol on IOP are reproducible across different studies and animal models, ensuring consistent and comparable results along with a well-documented safety profile (Seki et al. 2005 ) Methyldopa is a substrate (in the same manner as L-dopa) for the enzyme (dopamine beta-hydroxylase) that synthesizes noradrenaline/norepinephrine which is expressed in the blood-retinal barrier, cornea, and intestinal wall. Alpha-methyl noradrenaline selectively stimulates the α2-adrenoceptor thus inhibiting norepinephrine release (Puris et al. 2020 ). Furthermore, MD is metabolized to methyl-dopamine, which acts as an α2 receptor agonist (Damico et al. 2012 ). The study revealed that topical methyldopa twice daily was found to have a lowering effect on the rising IOP after betamethasone administration in a dose-dependent manner [Figure (4A)]. Chemical messengers and receptors in the CNS are similar to those in the periphery. α-methyl noradrenaline is not metabolized by monoamine oxidase and selectively stimulates α2-adrenergic receptors. Methyldopa acts in the same way as clonidine. This mechanism of action of methyldopa may be responsible for its IOP-lowering effect by decreasing AH production (Mori et al. 2024 ). Brimonidine and apraclonidine are α2-adrenergic agonists that lower intraocular pressure by reducing aqueous humor production. Brimonidine has a higher selectivity for α2 receptors than apraclonidine (Mikael 2007). Petursson et al. in a 1984 study showed that 16 open-angle glaucoma patients in a double-blind crossover study received a single dose of regular eye drops (70 µl) or mini-eye drops (15 µl) at concentrations of 0% (placebo), 0.25%, and 0.5% clonidine hydrochloride respectively was administered. Regular and mini drops with drug concentrations of 0.25% and 0.5%, respectively, significantly reduced intraocular pressure over 5 hours compared with placebo (Petursson et al. 1984 ). A recently published study by Mori et al investigating certain hit compounds that can protect from retinal damage and cerebrovascular diseases demonstrated that among their investigated hit compounds was alpha-methyldopa, which showed good protection from retinal damage based on its main mechanism of action which is α2-adrenoceptor agonist; furthermore, it was found that the retinal-protective effect was by inhibiting lipid radical generation, accumulation of oxidized products, and complement system activation that resulted from light exposure (Mori et al. 2024 ). These explanations highlight the observed ocular hypotensive effect produced by MD ophthalmic preparation where the best IOP reduction was observed at a concentration of 2% with a 24.2% reduction in the mean IOP. Conclusion The study outcome revealed that methyldopa managed to reduce the IOP in the chronic model of glaucoma and a concentration-dependent effect was observed with a profound reduction in the IOP seen in the concentration 2% MD, making MD a promising addition to the anti-glaucoma medications since its safety profile is well known and documented. Declarations Authors Contribution: The study idea and conceptualization, Kadhim HM & Abu-Raghif AR. Experimental work and data collection, Gatea FK. Manuscript preparation and statistical analysis, Hussein ZA. Final draft review and editing, Kadhim HM & Gatea FK. Competing Interest: The authors have no relevant financial or non-financial interests to disclose Funding: The authors declare that no funds, grants, or other support were received during the preparation of this manuscript Ethical Statement: This study's experimental requirements and procedures follow the National Center of the 3Rs (NC3Rs) and the ARRIVE 2.0 guidelines (Percie du Sert et al. 2020). An ethical statement was granted by the Institute Review Board (IRB) of the College of Medicine / Al-Nahrain University (issue no.: 20240901; Date: 8/10/2024) Data Availability: All data are included in the research paper and further access to supplementary results will be granted upon request from the authors References Azuara-Blanco A, Bgnasco L, Bagnis A, et al. (2020). Terminology and Guidelines for Glaucoma; European Glaucoma Society: Edinburgh, UK Trivli A, Koliarakis I, Terzidou C, et al. (2019). Normaltension glaucoma: Pathogenesis and genetics. Exp. Ther. Med., 17, 563–574. Leung DYL, Tham CC. (2022). Normal-tension glaucoma: Current concepts and approaches-A review. Clin. Exp. Ophthalmol., 50, 247–259. Tsai T, Reinehr S, Deppe L, et al. (2024). Glaucoma Animal Models beyond Chronic IOP Increase. Int. J. Mol. Sci., 25, 906. https://doi.org/10.3390/ijms25020906 Bell K, Und Hohenstein-Blaul NVT, Teister J, et al. (2018). Modulation of the Immune System for the Treatment of Glaucoma. Curr. Neuropharmacol., 16, 942–958. Karlstetter M, Scholz R, Rutar M, et al. (2015). Retinal microglia: Just bystander or target for therapy? Prog. Retin. Eye Res., 45, 30–57. Guan L, Li C, Zhang Y, et al. (2020). Puerarin ameliorates retinal ganglion cell damage induced by retinal ischemia/reperfusion through inhibiting the activation of TLR4/NLRP3 inflammasome. Life Sci., 256, 117935. Shu DY, Chaudhary S, Cho KS, et al. (2023). Role of Oxidative Stress in Ocular Diseases: A Balancing Act. Metabolites, 13, 187. Amato R. (2022). In vivo murine models for the study of glaucoma pathophysiology: procedures, analyses, and typical outcomes. Ann Eye Sci, 7, 30. https://dx.doi.org/10.21037/aes-21-48 Khaled Alsirhani, E, Abdulaziz Ali Y S, Mutlaq Ayidh Alosaimi S, et al. (2020). An Overview of Glaucoma Diagnosis & Management: A Literature Review. Arch Pharma Pract, 11(4):66-9. Leske MC, Heijl A, Hussein M, et al. (2003). Factors for glaucoma progression and the effect of treatment: the early manifest glaucoma trial. Arch Ophthalmol, 121: 48-56. Cordeiro MF, Gandolfi S, Gugleta K, et al. (2023). How latanoprost changed glaucoma management. Acta Ophthalmol. Percie du Sert N, Ahluwalia A, Alam S, et al. (2020). Reporting animal research: Explanation and elaboration for the ARRIVE guidelines 2.0. PLoS Biol, 18(7): e3000411. https://doi.org/10.1371/journal.pbio.3000411 Phulke S, Kaushik S, Kaur S, et al. (2017). Steroid-induced glaucoma: An avoidable irreversible blindness. J. Curr. Glaucoma Pract., 11, 67–72. Overby DR, Clark AF. (2015). Animal models of glucocorticoid-induced glaucoma. Exp. Eye Res., 141, 15–22. Nuyen B, Weinreb RN, Robbins SL. (2017). Steroid-induced glaucoma in the pediatric population. J. Am. Assoc. Pediatr. Ophthalmol. Strabismus, 21, 1–6. Noei M, Holoosadi M, & Anaraki-Ardakani H. (2017). Design of methyldopa structure and calculation of its properties by quantum mechanics. Arabian Journal of Chemistry, 10, S1923-S1937. https://doi.org/10.1016/j.arabjc.2013.07.021 Seremak-Mrozikiewicz A, Drews K. (2004). Methyldopa in therapy of hypertension in pregnant women. Ginekol. Pol., 75:160–165. Peter N Bennett, Morris J Brown, Pankaj Sharma. (2012). Clinical pharmacology; Churchill Livingstone,11th edition,995. Bogacz A, Mikołajczak P Ł, Wolek M, et al. (2021). Combined Effects of Methyldopa and Flavonoids on the Expression of Selected Factors Related to Inflammatory Processes and Vascular Diseases in Human Placenta Cells—An In Vitro Study. Molecules, 26(5). https://doi.org/10.3390/molecules26051259 Melena J, Santafé J, & Segarra J. (1998). The effect of topical diltiazem on the intraocular pressure in betamethasone-induced ocular hypertensive rabbits. The Journal of pharmacology and experimental therapeutics, 284(1), 278–282. Khan SU, Ashraf M, Salam A, et al. (2014). Steroid-induced ocular hypertension: an animal model. Gomal J Med Sci, 12: 115-7. Ahuja M. (2003). Ophthalmology Handbook. 1st ed. India Binding House. Delhi., Pp. 6-24, 145-163. Hussein MQ, Kadim HM, Abdulsahib WK. (2017). Effect of Telmisartan on Intra-Ocular Pressure in Induced Open Angle Glaucoma in Rabbits. International Journal of Science and Research (IJSR), 6(10): 1656-1661 Faul F, Erdfelder E, Lang AG, et al. (2007). G*Power 3: a flexible statistical power analysis program for the social, behavioral, and biomedical sciences. Behavior research methods., 39:175-191. https://doi.org/10.3758/bf03193146 Charan J, Kantharia ND. (2013). How to calculate sample size in animal studies? Journal of pharmacology & pharmacotherapeutics., 4:303-306. https://doi.org/10.4103/0976-500x.119726 Mansberger S L, Gordon M O, Jampel H, et al. (2012). Reduction in intraocular pressure after cataract extraction: The Ocular Hypertension Treatment Study. Ophthalmology, 119(9), 1826. https://doi.org/10.1016/j.ophtha.2012.02.050 Sun Y, Chen A, Zou M, et al. (2022). Time trends, associations and prevalence of blindness and vision loss due to glaucoma: an analysis of observational data from the Global Burden of Disease Study 2017. BMJ Open., 12(1):e053805. doi:10.1136/bmjopen-2021-053805 Harvey DH, Sugali CK, Mao W. (2024). Glucocorticoid-Induced Ocular Hypertension and Glaucoma. Clin Ophthalmol., 18:481-505 https://doi.org/10.2147/OPTH.S442749 Werner L, Chew J, Mamalis N. (2006). Experimental evaluation of ophthalmic devices and solutions using rabbit models. Vet. Ophthalmol., 9, 281–291. Evangelho K, & Mastronardi C A. (2019). Experimental Models of Glaucoma: A Powerful Translational Tool for the Future Development of New Therapies for Glaucoma in Humans—A Review of the Literature. Medicina, 55(6). https://doi.org/10.3390/medicina55060280 Abdulsahib WK, Abood SJ. (2021). The effect of Calcium channel blocker in the Betamethasone-induced Glaucoma model in rabbits. J Adv Pharm Educ Res., 11(1):135-40. https://doi.org/10.51847/2d3w8vfSVt Alwany AAK, Abu-Raghif AR, Rasheed AM. (2017). Effect of Bosentan on the Intraocular Pressure of Normal and Ocular-induced Hypertensive Rabbits. Int. J. Pharm. Sci. Rev. Res., 47(1), Article No. 15, Pages: 76-82 Hameed AH, Kadhim HM, Rasheed AM. (2020). The effects of topical adenosine agonists (Limonene) on induced ocular hypertension in rabbits. Journal of Global Pharma Technology, 12(1): 579-588 Sharif N A, Millar J C, Zode G, et al. (2024). Steroid-Induced Ocular Hypertension in Mice Is Differentially Reduced by Selective EP2, EP3, EP4, and IP Prostanoid Receptor Agonists. International Journal of Molecular Sciences, 25(6). https://doi.org/10.3390/ijms25063328 Abdulsahib WK, Al-Zubaidy A, Sahib HB, et al. (2015). Tolerable Ocular Hypotensive Effect of Topically Applied Sildenafil in Ocular in Normotensive and Betamethasone-Induced Hypertensive Rabbits.Int. J. Pharm. Sci. Rev. Res., 35(1), P: 96-102 Allen LV, Popovich NG and Ansel HC. (2005). Ansel’s Pharmaceutical Dosage Forms and Drug Delivery Systems. 8th ed. Lippincott Williams and Wilkins, Philadelphia. Pp. 540-569. Lee L-Y, Hsu J-H, Fu H-I, et al. (2022). Lowering the Intraocular Pressure in Rats and Rabbits by Cordyceps cicadae Extract and Its Active Compounds. Molecules., 27(3):707. https://doi.org/10.3390/molecules27030707 Prunte C. and Markstein R. (2000). Adrenergic regulation and its therapeutic aspects in the eye In: Orgul S., Flammer J. Pharmaco -therapy in Glaucoma, Pp. 73-78. Brian B. and Hoffman BB. (2007). Adrenoceptor Activation and other sympathomimetic Drugs. In: Katzung B.G. Basic and Clinical Pharmacology. 10th ed. McGraw Hill, Boston. Pp.126, 137,138. Gupta SK, Agarwal R, Galpalli ND, et al. (2007). Comparative efficacy of pilocarpine, timolol and latanoprost in experimental models of glaucoma. Methods Find Exp Clin Pharmacol, 29(10):665-71. Seki M, Tanaka T, Matsuda H, et al. (2005). Topically administered timolol and dorzolamide reduce intraocular pressure and protect retinal ganglion cells in a rat experimental glaucoma model. British Journal of Ophthalmology, 89:504-507. Puris E, Gynther M, Auriola S, et al. (2020). L-Type amino acid transporter 1 as a target for drug delivery, Pharm. Res., (N. Y.) 37 https://doi.org/10.1007/S11095-020-02826-8. Damico FM, Gasparin F, Scolari MR, et al. (2012). New approaches and potential treatments for dry age-related macular degeneration, Arq. Bras. Oftalmol., 75, 71–76, https://doi.org/10.1590/S0004-27492012000100016. Mori R, Abe M, Saimoto Y, et al. (2024). Construction of a screening system for lipid-derived radical inhibitors and validation of hit compounds to target retinal and cerebrovascular diseases. Redox Biology, 73, 103186. https://doi.org/10.1016/j.redox.2024.103186 Petursson G, Cole R, Hanna C. (1984). Treatment of Glaucoma Using Minidrops of Clonidine. Arch Ophthalmol., 102(8):1180–1181. doi:10.1001/archopht.1984.01040030958024 Jasim AH, Kadhim HM, Rasheed AM. (2019). Topical effects of atorvastatin on induced ocular hypertension in rabbits. Int. J. Biosci., 14(2):272-282. Jasim AH, KadimHM and Rasheed AM. (2019). Topical Effects of Metformin on Induced Ocular Hypertension in Rabbits. Indian Journal of Natural Sciences, 9 (52), 16723- 16734. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Published Journal Publication published 30 Oct, 2024 Read the published version in Naunyn-Schmiedeberg's Archives of Pharmacology → Version 1 posted Editorial decision: Revision requested 19 Oct, 2024 Reviews received at journal 18 Oct, 2024 Reviewers agreed at journal 12 Oct, 2024 Reviewers invited by journal 11 Oct, 2024 Editor assigned by journal 11 Oct, 2024 Submission checks completed at journal 11 Oct, 2024 First submitted to journal 09 Oct, 2024 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. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. 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-5234809","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":365403674,"identity":"9f4e6aca-3f96-4daa-85d2-f575814fd299","order_by":0,"name":"Foouad Kadhim Gatea","email":"","orcid":"","institution":"Nahrain University","correspondingAuthor":false,"prefix":"","firstName":"Foouad","middleName":"Kadhim","lastName":"Gatea","suffix":""},{"id":365403675,"identity":"d445b717-87de-4407-bd10-c48b068fcaff","order_by":1,"name":"Zeena Ayad Hussein","email":"data:image/png;base64,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","orcid":"","institution":"Nahrain University","correspondingAuthor":true,"prefix":"","firstName":"Zeena","middleName":"Ayad","lastName":"Hussein","suffix":""},{"id":365403676,"identity":"f7fb4b6b-6f45-4cd9-a923-3d01bbbe7703","order_by":2,"name":"Haitham Kadhim Mahmood","email":"","orcid":"","institution":"Nahrain University","correspondingAuthor":false,"prefix":"","firstName":"Haitham","middleName":"Kadhim","lastName":"Mahmood","suffix":""},{"id":365403677,"identity":"fe176785-8902-41cf-b149-4fb9b4dc25ad","order_by":3,"name":"ahmed rahmah abu-raghif","email":"","orcid":"","institution":"Nahrain University","correspondingAuthor":false,"prefix":"","firstName":"ahmed","middleName":"rahmah","lastName":"abu-raghif","suffix":""}],"badges":[],"createdAt":"2024-10-09 19:38:17","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-5234809/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-5234809/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s00210-024-03570-1","type":"published","date":"2024-10-30T16:20:26+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":66574523,"identity":"e5bf9d23-e96f-4353-a383-12ae690d9ed4","added_by":"auto","created_at":"2024-10-14 12:18:45","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":91970,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003estudy design timeline and flow chart\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eBID= twice daily, ED= eye drops, MD= methyldopa, DW= distilled water, IOP= intraocular pressure\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-5234809/v1/71a30b2064f5314e50742ec1.png"},{"id":66574526,"identity":"886482cd-263a-4c1b-80eb-1428410e6c76","added_by":"auto","created_at":"2024-10-14 12:18:45","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":160178,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eEffect of timolol and methyldopa on the IOP during the treatment timeline (7 days) compared to the induced and control groups.\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eResults are presented as mean ± SEM, n=8, and the significance level was set at (P≤0.05). (A) represents the effect of timolol, (B) the effect of timolol and 0.5% methyldopa, (C) the effect of timolol and 1% methyldopa, and (D) the effect of timolol and 2% methyldopa. * Comparison between groups, # Comparison within one group\u003c/p\u003e\n\u003cp\u003e*** or ### represents P≤0.001, ** or ## represents P≤0.01, * or # represents P≤0.05, ns= no significance\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-5234809/v1/501cbcb1a9eed21d03d02d48.png"},{"id":66574525,"identity":"163d2f1e-4869-47ed-938f-6da94681c19f","added_by":"auto","created_at":"2024-10-14 12:18:45","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":210973,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eEffect of the ocular agents on the changes in pupil diameter\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eResults were presented as mean ± SEM, n=8. There was no significant change among all groups. Induced IOP= received a weekly subconjunctival injection of betamethasone\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-5234809/v1/156a25c4f480ea27e4e64d58.png"},{"id":66574524,"identity":"00e85d5f-1f2e-44a1-8ba1-6a6978845b61","added_by":"auto","created_at":"2024-10-14 12:18:45","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":100035,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003ereduction of the IOP among treated groups. (A) a comparison in the effect of ocular treatments on the IOP level, and (B) the percentage reduction in IOP for the ocular treatments\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-5234809/v1/a058279f0e3b28b86ddfecc7.png"},{"id":68207238,"identity":"22b68cae-872b-4669-9701-f4695a7f6d11","added_by":"auto","created_at":"2024-11-04 16:36:05","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1017216,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-5234809/v1/f582a319-4595-40c5-9f7a-6bea9520fb88.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Effect of Ophthalmic Preparation of Methyldopa on Induced Ocular Hypertension in rabbits","fulltext":[{"header":"Introduction","content":"\u003cp\u003eGlaucoma is an eye disease characterized by progressive damage to the optic nerve and loss of retinal ganglion cells (RGCs) (Azuara-Blanco et al. \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). Eventually, this leads to blindness. A person with glaucoma can have either a primary or secondary cause. In primary open-angle glaucoma, nerve fibers in the retina and the optic nerve edge are lost, resulting in visual field defects. Risk factors for IOP elevation include elevated intraocular pressure (IOP) and advanced age (Leung and Tham \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). In normal-tension glaucoma (NTG), damage to the optic nerve and loss of RGCs occurs even if the intraocular pressure remains within the normal range (Trivli et al. \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). Secondary glaucoma conditions are caused by another ocular disease or health problem, such as injury, inflammation, or certain medications (Tsai et al. \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). The exact pathogenesis of the disease is still unknown. Excitotoxicity is thought to involve immunological mechanisms (Bell et al. \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2018\u003c/span\u003e), such as microglial inflammatory responses (Karlstetter et al. \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2015\u003c/span\u003e), ischemic processes (Guan et al., \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2020\u003c/span\u003e), and oxidative stress (Shu et al. \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). Elevated intraocular pressure (IOP) is considered the most common risk factor for the development and progression of glaucoma. It is an important pathophysiological factor for neurodegeneration and optic nerve damage (Amato \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). Although Mendelian inheritance occurs in a normal adult-onset form, heredity may play a role in Mendelian inheritance as the primary mode of inheritance (Khaled Alsirhani et al., \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). Lowering intraocular pressure is thought to help slow glaucoma damage to the optic nerve and visual field (Leske et al. \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2003\u003c/span\u003e). Lowering intraocular pressure has proven to be the only proven way to treat the disease effectively. Glaucoma medications, usually in the form of eye drops, are often the first treatment option as they reduce aqueous humor production or improve drainage (Cordeiro et al. \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). Other approaches, such as laser therapy and surgery, may also be options. The prevalence of glaucoma is significantly higher in older adults, especially those over 40 years of age, compared to younger people (Khaled Alsirhani et al. \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2020\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eIt is known that corticosteroids can cause ocular hypertension (OH) regardless of the route of administration (Phulke et al. \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). Significant increases in intraocular pressure can occur within hours or a few days after taking steroids. IOP usually normalizes once the medication is discontinued; however, this side effect may be irreversible in certain individuals (Overby and Clark \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). The precise mechanism by which corticosteroids increase intraocular pressure has yet to be elucidated. However, it is known that steroids cause stabilization of lysosomal membranes and accumulation of polymerized glycosaminoglycans within the trabecular meshwork (TM), creating a significant resistance to aqueous humor (AH) outflow. Furthermore, these agents also enhance TM resistance by increasing the expression of fibronectin, elastin, and laminin (Nuyen et al. \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2017\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eMethyldopa (MD) exerts its antihypertensive effect through a central mechanism involving biotransformation to methyl-norepinephrine (Seremak-Mrozikiewicz and Drews \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2004\u003c/span\u003e). Methyldopa is taken up by adrenergic neurons, where it is decarboxylated and hydroxylated to form the pseudo-neurotransmitter, methyl-noradrenaline, which has lower activity at α-receptors than norepinephrine and is, therefore, less effective at causing vasoconstriction (Noei et al. \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). α-Methyldopa has central and peripheral mechanisms of action. Only the L-isomer of α-methyldopa can inhibit dopa decarboxylase and remove norepinephrine from animal tissues. Methyldopa is reliably absorbed from the gastrointestinal tract and easily enters the central nervous system. It has a half-life of 1.5 hours (Peter 2012). Due to its safety profile for the fetus, it is considered the first-line antihypertensive drug for the treatment of preeclampsia during pregnancy. The most commonly associated side effects include sedation, nightmares, sexual dysfunction, and depression (Peter 2012; Bogacz et al. \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2021\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThis study evaluated the possible IOP-lowering effect of an ophthalmic preparation of methyldopa in corticosteroid-induced ocular hypertension in rabbits.\u003c/p\u003e"},{"header":"Materials \u0026 Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\n \u003ch2\u003eChemicals and Reagents:\u003c/h2\u003e\n \u003cp\u003eChemicals and drugs used in the study were purchased from different sources; methyldopa and benzalkonium chloride powders were purchased from (HyperChem, Hangzhou, China), betamethasone suspension ampule (Celestone\u0026reg; Chronodose\u0026reg;) containing betamethasone acetate 3mg and betamethasone sodium phosphate 3.9mg manufactured by (Schering Plough, Belgium), Xylazine HCl (XYL-M2, VMD \u0026reg; Livestock Pharma, Belgium). Ketamine HCl (Ketamine 10%, Alfasan Nederland BV, Holand). Tetracaine HCl 0.5% w/v eye drops (Alcon, USA). Tobramycin 0.3% w/v eye drops (Tobrex\u0026reg;, Alcon, USA). Timolol 0.5% w/v eye drops (Lithimole\u0026reg;, COOPER Pharmaceuticals, Greek).\u003c/p\u003e\n\u003c/div\u003e\n\u003ch3\u003ePreparation of Methyldopa Ophthalmic Drops:\u003c/h3\u003e\n\u003cp\u003eTwo solutions of 1/15M phosphate buffer with a pH of 7.4 were mixed in certain proportions to produce a phosphate buffer solution at pH (7.4). The first solution was prepared by dissolving 9.64 grams of sodium hydrogen phosphate in one litter of double-distilled water (DDW). The second solution was prepared by dissolving 8 g of sodium dihydrogen phosphate in one liter of DDW. One liter of a phosphate buffer solution was prepared by mixing 800 ml of the first and 200 ml of the second. 0.45 g of NaCl was added to make each 100 ml of phosphate-buffered solution isotonic.\u003c/p\u003e\n\u003cp\u003eAn ophthalmic solution of methyldopa was prepared by dissolving the desired amount of the tested drug powder in an appropriate volume of phosphate buffer solution with sufficient NaCl to make the solution isotonic. The mixture was stirred well with an ultrasonic shaker to enhance the dissolution followed by adding benzalkonium chloride solution and completing the final volume with a phosphate-buffered solution. The solution pH was adjusted to (7.4) by adding a few drops of phosphoric acid or sodium hydroxide solution. The final solution was filtered using a 0.22\u0026micro;m filter syringe to ensure clarity and sterility and then filled in previously autoclaved dropper containers (Allen et al. \u003cspan class=\"CitationRef\"\u003e2005\u003c/span\u003e), (Hameed et al. \u003cspan class=\"CitationRef\"\u003e2020\u003c/span\u003e). The formula used for the preparation of methyldopa ophthalmic solution was adapted from the British pharmacopeia for the preparation of a standard 0.3% ophthalmic agent that requires 0.3g of the test agent, 1% (v/v) of benzalkonium chloride solution, 0.45g of sodium chloride, and 1ml of absolute ethanol.\u003c/p\u003e\n\u003ch3\u003eExperimental Animals \u0026amp; Housing:\u003c/h3\u003e\n\u003cp\u003eThe study was conducted in the animal house of the College of Medicine / Al-Nahrain University. New Zealand albino male rabbits aged (5\u0026ndash;6) months weighing 1.5\u0026ndash;2 kg were purchased from the Al-Rhazi Center / Ministry of Industry and Minerals. Animals were housed in clean and sterile conditions with (23\u0026thinsp;+\u0026thinsp;2) \u0026deg;C temperature and humidity around 45%-, and a 12-hour light/night cycle and left to acclimatize to the new environment for one week with free access to water and food. Rabbits were kept in pairs per cage, cages were stainless steel, and provided enough clean substrate to permit the animal\u0026apos;s natural behavior. The cages were cleansed and washed every other day throughout the entire experiment. Rabbits\u0026apos; diet consisted mostly of standard pelleted balanced nutrition along with hay. Fresh greens including lettuce, parsley, and carrots were added to the diet three times weekly.\u003c/p\u003e\n\u003ch3\u003eStudy Design \u0026amp; Settings:\u003c/h3\u003e\n\u003cp\u003eThe experimental procedures were carried out in the animal handling room of the Department of Pharmacology / College of Medicine / Al-Nahrain University. 40 New Zealand White male rabbits were included in the experiment. The animals were divided randomly into 5 groups (n\u0026thinsp;=\u0026thinsp;8) applying a block randomization algorithm. In the control group; the animals received only isotonic buffer solution in the right eye and distilled water (DW) in the left eye without induction with betamethasone, the remaining 32 animals received a subconjunctival injection of betamethasone suspension (betamethasone acetate 3mg and betamethasone sodium phosphate 3.9mg) weekly over 21 days in both eyes to induce ocular hypertension. Animals were randomly assigned to the remaining treated groups; inclusion criteria were (animals with successful elevation in the IOP were included, whereas animals that failed to develop ocular hypertension or those showing signs of eye irritation and discharge were excluded and put in separate cages). Treatments were installed on day 24 of the induction. The remaining treated groups were; the timolol group (served as the standard treatment), in which animals received timolol 0.5% ED, the Methyldopa (MD) groups, which received different concentrations of MD ocular preparation (0.5%, 1%, and 2%) (Mori et al. \u003cspan class=\"CitationRef\"\u003e2024\u003c/span\u003e) respectively as illustrated in Figure (1).\u003c/p\u003e\n\u003cp\u003eAll treatments were given twice daily at 6-hour intervals (8:00 AM and 2:00 PM) in the right eye and DW in the left eye. Treatments were continued for 7 days, and all animals were subjected to the same handler throughout the experiment.\u003c/p\u003e\n\u003ch3\u003eInduction of Ocular Hypertension in Rabbits:\u003c/h3\u003e\n\u003cp\u003eThe protocol for inducing ocular hypertension was based on the method developed by Melena et al, with some adjustments. Melena et al observed that this model of induction closely resembles chronic open-angle glaucoma in humans (Melena et al. \u003cspan class=\"CitationRef\"\u003e1998\u003c/span\u003e). Rabbits were anesthetized through injection in the marginal ear with (ketamine HCl 60mg/kg and xylazine HCl 10mg/kg, IV). Using a micro-fine syringe, the animals were given a subconjunctival injection of 0.7 ml of betamethasone suspension (Khan et al. \u003cspan class=\"CitationRef\"\u003e2014\u003c/span\u003e). IOP measurements were conducted twice weekly to prevent damage to the corneal epithelium from frequent tonometry. The initial measurement was taken just before the weekly betamethasone subconjunctival injection, and the second measurement was taken three days after the injection. The animals received weekly betamethasone subconjunctival injections for a total of 21 days. The administration of the tested drugs began on the 24th day of betamethasone injection (three days after the fourth subconjunctival injection).\u003c/p\u003e\n\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\n \u003ch2\u003eMeasurement of Intraocular Pressure (IOP):\u003c/h2\u003e\n \u003cp\u003eCorneal local anesthesia was applied using 1\u0026ndash;2 drops of tetracaine HCL ophthalmic solution. The animal was held and restrained using a towel wrapped securely around its body. A Schiotz tonometer (Sartorius, Germany) was placed on the cornea. The IOP was measured 1 hour following the application of each test drug and an average of three readings was recorded. Before and after each measurement, the instrument was properly sterilized with 70% alcohol. As a prophylactic measure to prevent any opportunistic microbial infection by the device or during drug administration, an ophthalmic eye drop preparation of tobramycin 0.3% w/v was instilled twice (one time before the application of the device and again at the end of the measurement) (Jasim et al. \u003cspan class=\"CitationRef\"\u003e2019\u003c/span\u003e).\u003c/p\u003e\n\u003c/div\u003e\n\u003ch3\u003eDetermination of percentage of IOP reduction:\u003c/h3\u003e\n\u003cp\u003eTo help quantify the effectiveness of the treatment in reducing IOP in experimental glaucoma models, the following formula was applied to calculate the percentage of reduction in the IOP in an experimental study (Mansberger et al. \u003cspan class=\"CitationRef\"\u003e2012\u003c/span\u003e):\u003c/p\u003e\n\u003cdiv id=\"Equa\" class=\"Equation\"\u003e\n \u003cdiv class=\"mathdisplay\" id=\"FileID_Equa\" name=\"EquationSource\"\u003e$$\\:\\%\\:reduction=\\frac{\\text{b}\\text{a}\\text{s}\\text{e}\\text{l}\\text{i}\\text{n}\\text{e}\\:\\text{I}\\text{O}\\text{P}-\\text{p}\\text{o}\\text{s}\\text{t}\\:\\text{t}\\text{r}\\text{e}\\text{a}\\text{t}\\text{m}\\text{e}\\text{n}\\text{t}\\:\\text{I}\\text{O}\\text{P}}{\\text{b}\\text{a}\\text{s}\\text{e}\\text{l}\\text{i}\\text{n}\\text{e}\\:\\text{I}\\text{O}\\text{P}}\\:X\\:100$$\u003c/div\u003e\n\u003c/div\u003e\n\u003ch3\u003eAssessment of ocular reflexes:\u003c/h3\u003e\n\u003cp\u003ePupil diameter changes were measured using the pupil gauge penlight (Adelite\u0026trade;, American Diagnostic, USA). The results were presented in a millimeter unit (Ahuja \u003cspan class=\"CitationRef\"\u003e2003\u003c/span\u003e), (Alwany et al. \u003cspan class=\"CitationRef\"\u003e2017\u003c/span\u003e). The most important corneal reflexes are light, corneal local anesthetic effect, and conjunctival redness and lacrimation. The light reflex or pupillary response for both eyes was tested by swinging a flashlight to detect a relative afferent papillary defect. The corneal local anesthetic effect was tested using a wisp of cotton wool from the side. Finally, the conjunctiva of both eyes was examined for any signs of redness, swelling, and lacrimation. The observations for corneal reflexes were recorded as absent or present (Alwany et al. \u003cspan class=\"CitationRef\"\u003e2017\u003c/span\u003e).\u003c/p\u003e\n\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e\n \u003ch2\u003eSample Size calculation:\u003c/h2\u003e\n \u003cp\u003eThe sample size was determined utilizing the program G*Power for sample size calculation (Faul et al. \u003cspan class=\"CitationRef\"\u003e2007\u003c/span\u003e) based on Cohen\u0026rsquo;s principles (Charan and Kantharia \u003cspan class=\"CitationRef\"\u003e2013\u003c/span\u003e), post hoc analysis was used with an effect size of 0.5 and an alpha level of 0.05, F-family tests with a total \u0026lrm;sample size of 40 and each group of 8 animals.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec12\" class=\"Section2\"\u003e\n \u003ch2\u003eStatistical Analysis:\u003c/h2\u003e\n \u003cp\u003eData analysis was carried out utilizing GraphPad Prism 8.0. A paired t-test was used to compare the results before and after applying an agent in the right eye of a given group. A one-way analysis of variance (ANOVA), followed by a Tukey test comparison, was utilized to compare the groups. The level of significance was set at P\u0026thinsp;\u0026lt;\u0026thinsp;0.05. Data are presented as mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SEM (standard error of the mean).\u003c/p\u003e\n\u003c/div\u003e"},{"header":"Results","content":"\u003cp\u003eData analysis of the study revealed that the animals in the control group (normotensive) that received the non-medicated ocular preparation (vehicle) in the left eye didn\u0026rsquo;t exhibit any changes in the IOP and remained constant throughout the timeline of the treatment (7 days) and with normal ocular reflexes including (pupil diameter, no discharge or irritation, no lacrimation, active light reflex, and no local anesthetic effect) as demonstrated in figure (2A) and table (1).\u003c/p\u003e\n\u003cp\u003eAnimals in the remaining experimental groups that received weekly subconjunctival injections of betamethasone suspension in both eyes that were successfully included in the experiment managed to show a gradual elevation in the IOP by the end of the second week after the second injection with a peak elevation after the fourth injection resulting in an IOP as high as 24 mmHg which was statistically significant when compared to the control group (P\u0026thinsp;\u0026le;\u0026thinsp;0.001) as shown in figure (2).\u003c/p\u003e\n\u003cp\u003eAnimals that received the standard treatment of IOP (timolol 0.5%, ED) twice daily for seven days showed a gradual reduction in the IOP compared to the left eye that received only distilled water. The IOP in the right eye of the rabbits before starting the treatment was recorded (23.9\u0026thinsp;\u0026plusmn;\u0026thinsp;0.85 mmHg). Once treatment with timolol, 0.5% ED was initiated, a gradual reduction in the IOP was observed with a significant reduction (P\u0026thinsp;\u0026le;\u0026thinsp;0.05) observed on day 4 of the treatment by 3.7 mmHg and a maximum reduction in the IOP by 7.1 mmHg seen at the end of the experiment (day 7) with marked significant difference when compared to the left eye (P\u0026thinsp;\u0026le;\u0026thinsp;0.01) as shown in figure (2). Timolol 0.5% ED exhibited a percentage reduction in the IOP that reached 30% as shown in Figure (4B).\u003c/p\u003e\n\u003cp\u003eAnimals that received ophthalmic preparation of methyldopa with different concentrations (0.5%, 1%, and 2%) twice daily for seven days exhibited varying degrees of IOP reduction with percentages of 7.5, 18.3, and 24.2 respectively as shown in Figure (4B). The recorded IOP of the right eye treated with methyldopa groups before starting the treatment was (23.9\u0026thinsp;\u0026plusmn;\u0026thinsp;0.17, 24.5\u0026thinsp;\u0026plusmn;\u0026thinsp;0.49, and 24\u0026thinsp;\u0026plusmn;\u0026thinsp;0.74) for the selected methyldopa concentrations. As the methyldopa application was initiated, the animal group that received 0.5% of the preparation showed a reduction in IOP by 0.7 mmHg on day 4 of the treatment that was of no statistical significance (P\u0026thinsp;\u0026ge;\u0026thinsp;0.05) when compared to the left eye and then a maximum reduction in the IOP by 1.7 mmHg by the end of the experiment (day 7) that showed statistical significance (P\u0026thinsp;\u0026le;\u0026thinsp;0.05) compared to the left eye that received DW. On the other hand, animal groups that received 1% and 2% of MD preparation showed better outcomes, where there was a significant reduction in the IOP by (2.3 mmHg, P\u0026thinsp;\u0026le;\u0026thinsp;0.05) and (3.1 mmHg, P\u0026thinsp;\u0026le;\u0026thinsp;0.05) respectively on day 4 of the treatment with a maximum reduction in the IOP by (4.9 mmHg, P\u0026thinsp;\u0026le;\u0026thinsp;0.01) and (5.8 mmHg, P\u0026thinsp;\u0026le;\u0026thinsp;0.01) by the end of the experiment (day 7) when compared to the left eye that received DW as shown in figure (2B, 2C, and 2D).\u003c/p\u003e\n\u003cp\u003eCompared to the results of the standard (timolol 0.5%) group, animals that received MD 0.5% showed a significant difference but in favor of timolol (P\u0026thinsp;=\u0026thinsp;0.043), whereas the other groups that received MD 1% and 2% showed comparable outcomes to timolol with statistical significance of (P\u0026thinsp;=\u0026thinsp;0.739 and P\u0026thinsp;=\u0026thinsp;948) respectively as shown in figure (2C and 2D). MD showed a concentration-dependent reduction in the IOP among animal groups and the best outcome was observed in the animal group treated with MD 2% as observed in Figure (4A).\u003c/p\u003e\n\u003cp\u003eAnimal groups that received ophthalmic treatments with timolol 0.5% or MD didn\u0026rsquo;t show any changes in ocular reflexes, with pupil diameter remaining constant and unaffected among all animal groups [Figure (3)], an intact light reflex, an intact reflex to applying cotton wool (no local anesthetic effect), and no signs of irritation and lacrimation throughout the treatment timeline, as shown in Table (1).\u003c/p\u003e\n\u003cdiv class=\"gridtable\"\u003e\u0026nbsp;\u003ctable id=\"Tab1\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eEffect of the ocular agents on most important ocular reflexes\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003ccolgroup cols=\"6\"\u003e\u003c/colgroup\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\" rowspan=\"2\"\u003e\n \u003cp\u003eParameter\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colspan=\"5\"\u003e\n \u003cp\u003eTreatments\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eVehicle\u003c/strong\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eTimolol 0.5%\u003c/strong\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eMD 0.5%\u003c/strong\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eMD 1%\u003c/strong\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eMD 2%\u003c/strong\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eLacrimation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAbsent\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAbsent\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAbsent\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAbsent\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAbsent\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eConjunctival redness\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAbsent\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAbsent\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAbsent\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAbsent\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAbsent\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eLocal anesthetic effect\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAbsent\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAbsent\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAbsent\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAbsent\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAbsent\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eLight reflex\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePresent\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePresent\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePresent\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePresent\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePresent\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n\u003c/div\u003e\n\u003cp\u003eMD\u0026thinsp;=\u0026thinsp;methyldopa. Results were observational and only presented as (present or absent)\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eGlaucoma is the primary cause of irreversible blindness on a global scale (Sun et al. \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). Glucocorticoids are commonly used to treat immune-related and inflammatory conditions, but their chronic use, regardless of the administration method, can lead to various side effects, including the development of ocular hypertension. If left untreated, glucocorticoid-induced ocular hypertension may progress to glucocorticoid-induced glaucoma, resulting in the loss of retinal ganglion cells (Harvey et al. \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). The model of glucocorticoid-induced ocular hypertension in rabbits is widely used due to its simplicity in experimental development, easy maintenance, and cost-effectiveness, as highlighted by Evangelho et al. (2019). Glaucoma induced by corticosteroids in rabbits resembles primary open-angle glaucoma in humans (Werner et al. \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2006\u003c/span\u003e) and provides valuable insights into certain aspects of glaucoma pathology, given its anatomical and aqueous humor dynamics similarities with the human eye, as demonstrated in studies by Abdulsahib et al. (\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e2015\u003c/span\u003e), Evangelho et al. (2015), and Hameed et al. (\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2020\u003c/span\u003e), providing both morphological and molecular evidence of glaucoma's pathogenesis.\u003c/p\u003e \u003cp\u003eThe study showed that weekly subconjunctival administration of betamethasone resulted in mild elevation in the IOP within the first week of the administration with maximum and statistically significant elevation (P\u0026thinsp;\u0026le;\u0026thinsp;0.001) seen after the fourth administration with IOP (24\u0026thinsp;\u0026plusmn;\u0026thinsp;0.2) on day 24 of the experiment. These results were consistent with previous studies using a corticosteroid model for the induction of IOP (Khan et al. \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2014\u003c/span\u003e; Hussein et al. \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Jasim et al. \u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Abdulsahib and Abood \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Sharif et al. \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). It was speculated that the glaucoma effect produced by the chronic administration of glucocorticoids resulted from TM stiffness that hindered the outflow of the AH. Glucocorticoids cause TM stiffness by increasing the expression of transforming growth factor-β2 which in turn increases the extracellular matrix synthesis and deposition by activating the Smad2/3 pathway and other pathways leading to increased formation of TM cross-linked actin networks (CLANs), decreased cellularity of TM, and finally increased resistance to AH outflow from the canal of Schlemm (Harvey et al. \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2024\u003c/span\u003e; Sharif et al. \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2024\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eAlthough the eye is known to tolerate preparations of different pH, MD's ophthalmic preparation was still buffered to a pH close to that of the normal lacrimal fluid to minimize ocular irritation and discomfort. The addition of benzalkonium chloride was to enhance the effectiveness of the drug substance administered to the eye by modifying the penetration barrier of the cornea and promoting the adhesion of eye drops to the cornea; furthermore, the benzalkonium chloride acts as a preservative (Allen et al. \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e2005\u003c/span\u003e). This was proven by the control group's results, in which the animals received the ophthalmic vehicle only in the left eye and didn\u0026rsquo;t exhibit any significant changes (P\u0026thinsp;\u0026ge;\u0026thinsp;0.05) in the IOP or ocular reflexes.\u003c/p\u003e \u003cp\u003eThe epithelium, muscle, and vasculature of the ciliary body (CB) all contain nerve terminals. Within the ciliary epithelium (CE), there are α2 and β2 adrenergic receptors. Therefore, reducing aqueous humor (AH) formation can be achieved by stimulating the α-receptors or inhibiting the β-adrenergic receptors (Prunte and Markstein \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2000\u003c/span\u003e). When the β2-receptor in the ciliary body is stimulated, it leads to the stimulation of adenylyl cyclase, resulting in an increase in cyclic adenosine monophosphate (cAMP), which in turn increases AH production (Brain and Hoffman 2007). Timolol maleate 0.5% eye drops, a well-known non-selective β-adrenoceptor blocker approved as one of the treatment choices for mild to moderate open-angle glaucoma. Timolol was used as a standard (positive control) in this study to compare MD's effectiveness with, another adrenoceptor-acting agent, used as an ophthalmic preparation. The study showed that timolol 0.5% ED had a noticeable ocular hypotensive effect with a significant (P\u0026thinsp;\u0026le;\u0026thinsp;0.01) reduction in the mean IOP after one day of its application. It exhibited a marked decrease in the mean IOP on day 7 of the treatment, in which the final IOP showed no significant difference when compared to that of the normal group (P\u0026thinsp;\u0026ge;\u0026thinsp;0.05). These results were greatly supported by a previous finding done by Lee et al, where the study used timolol 0.5% ED as a positive control in the rabbit model of ocular hypertension and the results revealed that timolol managed to markedly reduce the IOP within 1\u0026ndash;2 hours post-application compared to the control (Lee et al. \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). Finally, based on these results, timolol 0.5% ED produced a 30% reduction in the mean IOP as shown in Figure (4B). The results of this study were consistent with previous findings done by Gupta et al, where the outcome of the study showed that timolol 0.5% managed to reduce mean IOP by 20% \u0026minus;\u0026thinsp;35% in ocular hypertensive eyes (Gupta et al. \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e2007\u003c/span\u003e). The effects of timolol on IOP are reproducible across different studies and animal models, ensuring consistent and comparable results along with a well-documented safety profile (Seki et al. \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e2005\u003c/span\u003e)\u003c/p\u003e \u003cp\u003eMethyldopa is a substrate (in the same manner as L-dopa) for the enzyme (dopamine beta-hydroxylase) that synthesizes noradrenaline/norepinephrine which is expressed in the blood-retinal barrier, cornea, and intestinal wall. Alpha-methyl noradrenaline selectively stimulates the α2-adrenoceptor thus inhibiting norepinephrine release (Puris et al. \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). Furthermore, MD is metabolized to methyl-dopamine, which acts as an α2 receptor agonist (Damico et al. \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e2012\u003c/span\u003e). The study revealed that topical methyldopa twice daily was found to have a lowering effect on the rising IOP after betamethasone administration in a dose-dependent manner [Figure (4A)].\u003c/p\u003e \u003cp\u003eChemical messengers and receptors in the CNS are similar to those in the periphery. α-methyl noradrenaline is not metabolized by monoamine oxidase and selectively stimulates α2-adrenergic receptors. Methyldopa acts in the same way as clonidine. This mechanism of action of methyldopa may be responsible for its IOP-lowering effect by decreasing AH production (Mori et al. \u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). Brimonidine and apraclonidine are α2-adrenergic agonists that lower intraocular pressure by reducing aqueous humor production. Brimonidine has a higher selectivity for α2 receptors than apraclonidine (Mikael 2007). Petursson et al. in a 1984 study showed that 16 open-angle glaucoma patients in a double-blind crossover study received a single dose of regular eye drops (70 \u0026micro;l) or mini-eye drops (15 \u0026micro;l) at concentrations of 0% (placebo), 0.25%, and 0.5% clonidine hydrochloride respectively was administered. Regular and mini drops with drug concentrations of 0.25% and 0.5%, respectively, significantly reduced intraocular pressure over 5 hours compared with placebo (Petursson et al. \u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e1984\u003c/span\u003e). A recently published study by Mori et al investigating certain hit compounds that can protect from retinal damage and cerebrovascular diseases demonstrated that among their investigated hit compounds was alpha-methyldopa, which showed good protection from retinal damage based on its main mechanism of action which is α2-adrenoceptor agonist; furthermore, it was found that the retinal-protective effect was by inhibiting lipid radical generation, accumulation of oxidized products, and complement system activation that resulted from light exposure (Mori et al. \u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). These explanations highlight the observed ocular hypotensive effect produced by MD ophthalmic preparation where the best IOP reduction was observed at a concentration of 2% with a 24.2% reduction in the mean IOP.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eThe study outcome revealed that methyldopa managed to reduce the IOP in the chronic model of glaucoma and a concentration-dependent effect was observed with a profound reduction in the IOP seen in the concentration 2% MD, making MD a promising addition to the anti-glaucoma medications since its safety profile is well known and documented.\u0026nbsp;\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAuthors Contribution:\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe study idea and conceptualization, Kadhim HM \u0026amp; Abu-Raghif AR. Experimental work and data collection, Gatea FK. Manuscript preparation and statistical analysis, Hussein ZA. Final draft review and editing, Kadhim HM \u0026amp; Gatea FK.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting Interest:\u003c/strong\u003e The authors have no relevant financial or non-financial interests to disclose\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding:\u003c/strong\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe authors declare that no funds, grants, or other support were received during the preparation of this manuscript\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthical Statement: \u0026nbsp;\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study\u0026apos;s experimental requirements and procedures follow the National Center of the 3Rs (NC3Rs) and the ARRIVE 2.0 guidelines (Percie du Sert et al. 2020). An ethical statement was granted by the Institute Review Board (IRB) of the College of Medicine / Al-Nahrain University (issue no.: 20240901; Date: 8/10/2024)\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData Availability:\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll data are included in the research paper and further access to supplementary results will be granted upon request from the authors\u0026nbsp;\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eAzuara-Blanco A, Bgnasco L, Bagnis A, et al. (2020). Terminology and Guidelines for Glaucoma; European Glaucoma Society: Edinburgh, UK\u003c/li\u003e\n\u003cli\u003eTrivli A, Koliarakis I, Terzidou C, et al. (2019). Normaltension glaucoma: Pathogenesis and genetics. Exp. Ther. Med., 17, 563\u0026ndash;574.\u003c/li\u003e\n\u003cli\u003eLeung DYL, Tham CC. (2022). Normal-tension glaucoma: Current concepts and approaches-A review. Clin. Exp. Ophthalmol., 50, 247\u0026ndash;259. \u003c/li\u003e\n\u003cli\u003eTsai T, Reinehr S, Deppe L, et al. (2024). Glaucoma Animal Models beyond Chronic IOP Increase. Int. J. Mol. Sci., 25, 906. https://doi.org/10.3390/ijms25020906 \u003c/li\u003e\n\u003cli\u003eBell K, Und Hohenstein-Blaul NVT, Teister J, et al. (2018). Modulation of the Immune System for the Treatment of Glaucoma. Curr. Neuropharmacol., 16, 942\u0026ndash;958.\u003c/li\u003e\n\u003cli\u003eKarlstetter M, Scholz R, Rutar M, et al. (2015). Retinal microglia: Just bystander or target for therapy? Prog. Retin. Eye Res., 45, 30\u0026ndash;57.\u003c/li\u003e\n\u003cli\u003eGuan L, Li C, Zhang Y, et al. (2020). Puerarin ameliorates retinal ganglion cell damage induced by retinal ischemia/reperfusion through inhibiting the activation of TLR4/NLRP3 inflammasome. Life Sci., 256, 117935.\u003c/li\u003e\n\u003cli\u003eShu DY, Chaudhary S, Cho KS, et al. (2023). Role of Oxidative Stress in Ocular Diseases: A Balancing Act. Metabolites, 13, 187.\u003c/li\u003e\n\u003cli\u003eAmato R. (2022). In vivo murine models for the study of glaucoma pathophysiology: procedures, analyses, and typical outcomes. Ann Eye Sci, 7, 30. https://dx.doi.org/10.21037/aes-21-48 \u003c/li\u003e\n\u003cli\u003eKhaled Alsirhani, E, Abdulaziz Ali Y S, Mutlaq Ayidh Alosaimi S, et al. (2020). An Overview of Glaucoma Diagnosis \u0026amp; Management: A Literature Review. Arch Pharma Pract, 11(4):66-9.\u003c/li\u003e\n\u003cli\u003eLeske MC, Heijl A, Hussein M, et al. (2003). Factors for glaucoma progression and the effect of treatment: the early manifest glaucoma trial. Arch Ophthalmol, 121: 48-56.\u003c/li\u003e\n\u003cli\u003eCordeiro MF, Gandolfi S, Gugleta K, et al. (2023). How latanoprost changed glaucoma management. Acta Ophthalmol.\u003c/li\u003e\n\u003cli\u003ePercie du Sert N, Ahluwalia A, Alam S, et al. (2020). Reporting animal research: Explanation and elaboration for the ARRIVE guidelines 2.0. PLoS Biol, 18(7): e3000411. https://doi.org/10.1371/journal.pbio.3000411 \u003c/li\u003e\n\u003cli\u003ePhulke S, Kaushik S, Kaur S, et al. (2017). Steroid-induced glaucoma: An avoidable irreversible blindness. J. Curr. Glaucoma Pract., 11, 67\u0026ndash;72.\u003c/li\u003e\n\u003cli\u003eOverby DR, Clark AF. (2015). Animal models of glucocorticoid-induced glaucoma. Exp. Eye Res., 141, 15\u0026ndash;22.\u003c/li\u003e\n\u003cli\u003eNuyen B, Weinreb RN, Robbins SL. (2017). Steroid-induced glaucoma in the pediatric population. J. Am. Assoc. Pediatr. Ophthalmol. Strabismus, 21, 1\u0026ndash;6.\u003c/li\u003e\n\u003cli\u003eNoei M, Holoosadi M, \u0026amp; Anaraki-Ardakani H. (2017). Design of methyldopa structure and calculation of its properties by quantum mechanics. Arabian Journal of Chemistry, 10, S1923-S1937. https://doi.org/10.1016/j.arabjc.2013.07.021\u003c/li\u003e\n\u003cli\u003eSeremak-Mrozikiewicz A, Drews K. (2004). Methyldopa in therapy of hypertension in pregnant women. Ginekol. Pol., 75:160\u0026ndash;165.\u003c/li\u003e\n\u003cli\u003ePeter N Bennett, Morris J Brown, Pankaj Sharma. (2012). Clinical pharmacology; Churchill Livingstone,11th edition,995.\u003c/li\u003e\n\u003cli\u003eBogacz A, Mikołajczak P Ł, Wolek M, et al. (2021). Combined Effects of Methyldopa and Flavonoids on the Expression of Selected Factors Related to Inflammatory Processes and Vascular Diseases in Human Placenta Cells\u0026mdash;An In Vitro Study. Molecules, 26(5). https://doi.org/10.3390/molecules26051259 \u003c/li\u003e\n\u003cli\u003eMelena J, Santaf\u0026eacute; J, \u0026amp; Segarra J. (1998). The effect of topical diltiazem on the intraocular pressure in betamethasone-induced ocular hypertensive rabbits. The Journal of pharmacology and experimental therapeutics, 284(1), 278\u0026ndash;282.\u003c/li\u003e\n\u003cli\u003eKhan SU, Ashraf M, Salam A, et al. (2014). Steroid-induced ocular hypertension: an animal model. Gomal J Med Sci, 12: 115-7.\u003c/li\u003e\n\u003cli\u003eAhuja M. (2003). Ophthalmology Handbook. 1st ed. India Binding House. Delhi., Pp. 6-24, 145-163.\u003c/li\u003e\n\u003cli\u003eHussein MQ, Kadim HM, Abdulsahib WK. (2017). Effect of Telmisartan on Intra-Ocular Pressure in Induced Open Angle Glaucoma in Rabbits. International Journal of Science and Research (IJSR), 6(10): 1656-1661\u003c/li\u003e\n\u003cli\u003eFaul F, Erdfelder E, Lang AG, et al. (2007). G*Power 3: a flexible statistical power analysis program for the social, behavioral, and biomedical sciences. Behavior research methods., 39:175-191. https://doi.org/10.3758/bf03193146 \u003c/li\u003e\n\u003cli\u003eCharan J, Kantharia ND. (2013). How to calculate sample size in animal studies? Journal of pharmacology \u0026amp; pharmacotherapeutics., 4:303-306. https://doi.org/10.4103/0976-500x.119726 \u003c/li\u003e\n\u003cli\u003eMansberger S L, Gordon M O, Jampel H, et al. (2012). Reduction in intraocular pressure after cataract extraction: The Ocular Hypertension Treatment Study. Ophthalmology, 119(9), 1826. https://doi.org/10.1016/j.ophtha.2012.02.050\u003c/li\u003e\n\u003cli\u003eSun Y, Chen A, Zou M, et al. (2022). Time trends, associations and prevalence of blindness and vision loss due to glaucoma: an analysis of observational data from the Global Burden of Disease Study 2017. BMJ Open., 12(1):e053805. doi:10.1136/bmjopen-2021-053805 \u003c/li\u003e\n\u003cli\u003eHarvey DH, Sugali CK, Mao W. (2024). Glucocorticoid-Induced Ocular Hypertension and Glaucoma. Clin Ophthalmol., 18:481-505 https://doi.org/10.2147/OPTH.S442749\u003c/li\u003e\n\u003cli\u003eWerner L, Chew J, Mamalis N. (2006). Experimental evaluation of ophthalmic devices and solutions using rabbit models. Vet. Ophthalmol., 9, 281\u0026ndash;291.\u003c/li\u003e\n\u003cli\u003eEvangelho K, \u0026amp; Mastronardi C A. (2019). Experimental Models of Glaucoma: A Powerful Translational Tool for the Future Development of New Therapies for Glaucoma in Humans\u0026mdash;A Review of the Literature. Medicina, 55(6). https://doi.org/10.3390/medicina55060280\u003c/li\u003e\n\u003cli\u003eAbdulsahib WK, Abood SJ. (2021). The effect of Calcium channel blocker in the Betamethasone-induced Glaucoma model in rabbits. J Adv Pharm Educ Res., 11(1):135-40. https://doi.org/10.51847/2d3w8vfSVt\u003c/li\u003e\n\u003cli\u003eAlwany AAK, Abu-Raghif AR, Rasheed AM. (2017). Effect of Bosentan on the Intraocular Pressure of Normal and Ocular-induced Hypertensive Rabbits. Int. J. Pharm. Sci. Rev. Res., 47(1), Article No. 15, Pages: 76-82 \u003c/li\u003e\n\u003cli\u003eHameed AH, Kadhim HM, Rasheed AM. (2020). The effects of topical adenosine agonists (Limonene) on induced ocular hypertension in rabbits. Journal of Global Pharma Technology, 12(1): 579-588\u003c/li\u003e\n\u003cli\u003eSharif N A, Millar J C, Zode G, et al. (2024). Steroid-Induced Ocular Hypertension in Mice Is Differentially Reduced by Selective EP2, EP3, EP4, and IP Prostanoid Receptor Agonists. International Journal of Molecular Sciences, 25(6). https://doi.org/10.3390/ijms25063328\u003c/li\u003e\n\u003cli\u003eAbdulsahib WK, Al-Zubaidy A, Sahib HB, et al. (2015). Tolerable Ocular Hypotensive Effect of Topically Applied Sildenafil in Ocular in Normotensive and Betamethasone-Induced Hypertensive Rabbits.Int. J. Pharm. Sci. Rev. Res., 35(1), P: 96-102\u003c/li\u003e\n\u003cli\u003eAllen LV, Popovich NG and Ansel HC. (2005). Ansel\u0026rsquo;s Pharmaceutical Dosage Forms and Drug Delivery Systems. 8th ed. Lippincott Williams and Wilkins, Philadelphia. Pp. 540-569.\u003c/li\u003e\n\u003cli\u003eLee L-Y, Hsu J-H, Fu H-I, et al. (2022). Lowering the Intraocular Pressure in Rats and Rabbits by Cordyceps cicadae Extract and Its Active Compounds. Molecules., 27(3):707. https://doi.org/10.3390/molecules27030707\u003c/li\u003e\n\u003cli\u003ePrunte C. and Markstein R. (2000). Adrenergic regulation and its therapeutic aspects in the eye In: Orgul S., Flammer J. Pharmaco -therapy in Glaucoma, Pp. 73-78.\u003c/li\u003e\n\u003cli\u003eBrian B. and Hoffman BB. (2007). Adrenoceptor Activation and other sympathomimetic Drugs. In: Katzung B.G. Basic and Clinical Pharmacology. 10th ed. McGraw Hill, Boston. Pp.126, 137,138.\u003c/li\u003e\n\u003cli\u003eGupta SK, Agarwal R, Galpalli ND, et al. (2007). Comparative efficacy of pilocarpine, timolol and latanoprost in experimental models of glaucoma. Methods Find Exp Clin Pharmacol, 29(10):665-71.\u003c/li\u003e\n\u003cli\u003eSeki M, Tanaka T, Matsuda H, et al. (2005). Topically administered timolol and dorzolamide reduce intraocular pressure and protect retinal ganglion cells in a rat experimental glaucoma model. British Journal of Ophthalmology, 89:504-507.\u003c/li\u003e\n\u003cli\u003ePuris E, Gynther M, Auriola S, et al. (2020). L-Type amino acid transporter 1 as a target for drug delivery, Pharm. Res., (N. Y.) 37 https://doi.org/10.1007/S11095-020-02826-8.\u003c/li\u003e\n\u003cli\u003eDamico FM, Gasparin F, Scolari MR, et al. (2012). New approaches and potential treatments for dry age-related macular degeneration, Arq. Bras. Oftalmol., 75, 71\u0026ndash;76, https://doi.org/10.1590/S0004-27492012000100016.\u003c/li\u003e\n\u003cli\u003eMori R, Abe M, Saimoto Y, et al. (2024). Construction of a screening system for lipid-derived radical inhibitors and validation of hit compounds to target retinal and cerebrovascular diseases. Redox Biology, 73, 103186. https://doi.org/10.1016/j.redox.2024.103186\u003c/li\u003e\n\u003cli\u003ePetursson G, Cole R, Hanna C. (1984). Treatment of Glaucoma Using Minidrops of Clonidine. Arch Ophthalmol., 102(8):1180\u0026ndash;1181. doi:10.1001/archopht.1984.01040030958024\u003c/li\u003e\n\u003cli\u003eJasim AH, Kadhim HM, Rasheed AM. (2019). Topical effects of atorvastatin on induced ocular hypertension in rabbits. Int. J. Biosci., 14(2):272-282. \u003c/li\u003e\n\u003cli\u003eJasim AH, KadimHM and Rasheed AM. (2019). Topical Effects of Metformin on Induced Ocular Hypertension in Rabbits. Indian Journal of Natural Sciences, 9 (52), 16723- 16734.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"naunyn-schmiedebergs-archives-of-pharmacology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"nsap","sideBox":"Learn more about [Naunyn-Schmiedeberg's Archives of Pharmacology](https://www.springer.com/journal/210)","snPcode":"210","submissionUrl":"https://submission.nature.com/new-submission/210/3","title":"Naunyn-Schmiedeberg's Archives of Pharmacology","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Glaucoma, Corticosteroids, Methyldopa, Timolol, Intraocular pressure, Rabbits ","lastPublishedDoi":"10.21203/rs.3.rs-5234809/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-5234809/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eGlaucoma is a type of ocular disorder with multifaceted etiologies characterized by progressive optic nerve damage and ultimately loss of visual field. This study evaluated the possible IOP-lowering effect of an ophthalmic preparation of methyldopa in corticosteroid-induced ocular hypertension in rabbits. 40 New Zealand white male rabbits were assigned to the experiment and then randomly divided into 5 groups (n\u0026thinsp;=\u0026thinsp;8). Ocular hypertension was induced by weekly subconjunctival injection of betamethasone suspension in both eyes. Animal groups included the control (healthy) group, which received the ophthalmic vehicle only, the standard (timolol) group, which received 0.5% timolol ED, and the MD groups, which received 0.5%, 1%, and 2% of methyldopa ophthalmic preparation. Treatments were applied to the right eye twice daily for 7 days whereas the left eye served as control and was given only distilled water. IOP was recorded and ocular reflexes were observed. Weekly subconjunctival injections of betamethasone resulted in a significant elevation in the IOP (P\u0026thinsp;\u0026le;\u0026thinsp;0.001) that was reduced after treatments with timolol 0.5% and MD at different concentrations. Timolol showed the highest reduction (P\u0026thinsp;\u0026le;\u0026thinsp;0.001) in the mean IOP with a 30% reduction. MD showed a concentration-dependent reduction with the highest reduction (P\u0026thinsp;\u0026le;\u0026thinsp;0.01) observed at 2% compared to the induced/DW eyes and no significant difference compared to the timolol 0.5% (P\u0026thinsp;\u0026ge;\u0026thinsp;0.05) with a 24.2% reduction in the mean IOP. Methyldopa managed to reduce the IOP in the chronic model of glaucoma, making MD a promising addition to the anti-glaucoma medications.\u003c/p\u003e","manuscriptTitle":"Effect of Ophthalmic Preparation of Methyldopa on Induced Ocular Hypertension in rabbits","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-10-14 12:18:40","doi":"10.21203/rs.3.rs-5234809/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2024-10-19T15:02:56+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2024-10-18T20:05:41+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"36176996681228369973430513156160563222","date":"2024-10-12T19:52:29+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2024-10-11T10:17:38+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2024-10-11T07:58:48+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2024-10-11T07:58:35+00:00","index":"","fulltext":""},{"type":"submitted","content":"Naunyn-Schmiedeberg's Archives of Pharmacology","date":"2024-10-09T19:32:10+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"naunyn-schmiedebergs-archives-of-pharmacology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"nsap","sideBox":"Learn more about [Naunyn-Schmiedeberg's Archives of Pharmacology](https://www.springer.com/journal/210)","snPcode":"210","submissionUrl":"https://submission.nature.com/new-submission/210/3","title":"Naunyn-Schmiedeberg's Archives of Pharmacology","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"c3efc158-fd4d-4c39-a3c9-292547cff279","owner":[],"postedDate":"October 14th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2024-11-04T16:28:38+00:00","versionOfRecord":{"articleIdentity":"rs-5234809","link":"https://doi.org/10.1007/s00210-024-03570-1","journal":{"identity":"naunyn-schmiedebergs-archives-of-pharmacology","isVorOnly":false,"title":"Naunyn-Schmiedeberg's Archives of Pharmacology"},"publishedOn":"2024-10-30 16:20:26","publishedOnDateReadable":"October 30th, 2024"},"versionCreatedAt":"2024-10-14 12:18:40","video":"","vorDoi":"10.1007/s00210-024-03570-1","vorDoiUrl":"https://doi.org/10.1007/s00210-024-03570-1","workflowStages":[]},"version":"v1","identity":"rs-5234809","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-5234809","identity":"rs-5234809","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}