Adverse Reactions to Protamine: A Study Based on the FAERS Database and Bibliometric Analysis

Adverse Reactions to Protamine: A Study Based on the FAERS Database and Bibliometric Analysis | Authorea try { document.documentElement.classList.add('js'); } catch (e) { } var _gaq = _gaq || []; _gaq.push(['_setAccount', 'G-8VDV14Y67G']); _gaq.push(['_trackPageview']); (function() { var ga = document.createElement('script'); ga.type = 'text/javascript'; ga.async = true; ga.src = ('https:' == document.location.protocol ? 'https://ssl' : 'http://www') + '.google-analytics.com/ga.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(ga, s); })(); Skip to main content Preprints Collections Wiley Open Research IET Open Research Ecological Society of Japan All Collections About About Authorea FAQs Contact Us Quick Search anywhere Search for preprint articles, keywords, etc. Search Search ADVANCED SEARCH SCROLL This is a preprint and has not been peer reviewed. Data may be preliminary. 11 February 2026 V1 Latest version Share on Adverse Reactions to Protamine: A Study Based on the FAERS Database and Bibliometric Analysis Authors : weitong wu , Qian Guo , Xiaopeng Ma , and Tengyue Zhao [email protected] Authors Info & Affiliations https://doi.org/10.22541/au.177084046.62985429/v1 240 views 102 downloads Contents Abstract Supplementary Material Information & Authors Metrics & Citations View Options References Figures Tables Media Share Abstract Background: Protamine, the only antidote for unfractionated heparin, is crucial in cardiac and vascular surgery, but carries a significant risk of adverse drug events (ADEs). However, a comprehensive real-world safety profile is lacking. This study aimed to evaluate protamine-associated ADEs through data mining of the FDA Adverse Event Reporting System (FAERS) and bibliometric analysis. Methods: The FAERS database from Q1 2004 to Q4 2024 contained adverse event reports including protamine as the main suspect. Four algorithms—ROR, PRR, BCPNN, and MGPS—were used to investigate disproportionality to find relevant signals. A Web of Science Core Collection (WoSCC) bibliometric study identified research patterns. Results: Analysis of 512 protamine adverse event reports revealed 58 significant signals impacting 12 System Organ Classes(SOCs). Cardiac disorders constituted the most prevalent category, followed by investigations and vascular disorders. Confirmed risks encompassed recognized reactions including hypotension, pulmonary hypertension, bronchospasm, and anaphylaxis. Unexpected signals comprised resuscitation, heparin-induced thrombocytopenia, unresponsive to stimuli and product quality issues. Bibliometric analysis indicated a focused research emphasis on immune-related adverse events linked to nph insulin and adverse events associated with heparin. Conclusion: This research confirms known risks and identifies novel safety signals for protamine, underscoring the need for improved risk stratification, individualized dosing, and development of safer reversal agents. Weitong Wu 1† , Qian Guo 2† , Xiaopeng Ma 1 ,Tengyue Zhao 1,3* 1School of Basic Medical Sciences, Hebei Medical University, Shijiazhuang,050000,China 2Department of Rhinology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou,450052, China 3Department of Cardiovascular Surgery，The Second hospital of Hebei Medical University，Shijiazhuang,050000, China * Correspondence: Tengyue Zhao, [email protected] Department of Cardiovascular Surgery，The Second hospital of Hebei Medical University，Shijiazhuang 050000, China; School of Basic Medical Sciences, Hebei Medical University, Shijiazhuang 050000, China †These authors have contributed equally to this work All authors contributed to the study conception and design. Material preparation, data collection and analysis were performed by [Weitong Wu], [Qian Guo],[Xiaopeng Ma]and [Tengyue Zhao]. The first draft of the manuscript was written by [Weitong Wu] and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript. Date will be made available on requestfrom the corresponding author [Tengyue Zhao] on reasonable request. Disclosure: The authors declare no confict of interest. Funding Declaration: Hebei Provincial Department of Finance Government Funding or Public hospital reform and high-quality development demonstration project (No.36) Ethics declaration: not applicable Keywords: protamine; adverse events; FAERS; Bibliometric analysis; pharmacovigilance study Abstract Background: Protamine, the only antidote for unfractionated heparin, is crucial in cardiac and vascular surgery, but carries a significant risk of adverse drug events (ADEs). However, a comprehensive real-world safety profile is lacking. This study aimed to evaluate protamine-associated ADEs through data mining of the FDA Adverse Event Reporting System (FAERS) and bibliometric analysis. Methods: The FAERS database from Q1 2004 to Q4 2024 contained adverse event reports including protamine as the main suspect. Four algorithms—ROR, PRR, BCPNN, and MGPS—were used to investigate disproportionality to find relevant signals. A Web of Science Core Collection (WoSCC) bibliometric study identified research patterns. Results: Analysis of 512 protamine adverse event reports revealed 58 significant signals impacting 12 System Organ Classes(SOCs). Cardiac disorders constituted the most prevalent category, followed by investigations and vascular disorders. Confirmed risks encompassed recognized reactions including hypotension, pulmonary hypertension, bronchospasm, and anaphylaxis. Unexpected signals comprised resuscitation, heparin-induced thrombocytopenia, unresponsive to stimuli and product quality issues. Bibliometric analysis indicated a focused research emphasis on immune-related adverse events linked to nph insulin and adverse events associated with heparin. Conclusion: This research confirms known risks and identifies novel safety signals for protamine, underscoring the need for improved risk stratification, individualized dosing, and development of safer reversal agents. Key Points: 1.Novel methodology integrating FAERS data mining with bibliometric analysis provides a comprehensive real-world safety profile of protamine 2.New safety signals, including heparin-induced thrombocytopenia,altered therapeutic effects and unresponsive to stimuli, are identified beyond known risks. 3.Bibliometric analysis maps the research evolution, showing a shift from fundamental mechanisms to clinical studies, with NPH insulin and heparin as persistent foci. 4.Findings support improved preoperative risk assessment and development of safer heparin reversal alternatives. Plain Language Summary : Protamine is a medication used to reverse the effects of heparin, a blood thinner commonly given during heart and vascular surgeries. While it can save lives, protamine itself sometimes causes serious side effects. In this study, we analyzed real-world safety reports and scientific publications to better understand these risks. We confirmed known dangers, such as severe drops in blood pressure, lung problems, and allergic reactions. We also identified previously unreported risks, including resuscitation, heparin-induced thrombocytopenia, unresponsive to stimuli and product quality issues.Bibliometric analysis maps the research evolution, showing a shift from fundamental mechanisms to clinical studies, with NPH insulin and heparin as persistent foci.Our results suggest that doctors should assess patients more carefully before surgery, adjust doses individually, and consider developing safer alternatives to protamine to improve patient safety. Introduction Protamine sulfate, a cationic polypeptide derived from salmon sperm 1 , remains the cornerstone agent for reversing heparin-induced anticoagulation during cardiac surgery, vascular interventions, and dialysis 2.3 . Despite its critical role, protamine administration is associated with a spectrum of potentially serious adverse drug events (ADEs), including hypotension, bradycardia, pulmonary hypertension, and anaphylactic reactions 4.5 . Current safety knowledge primarily stems from clinical trials and case reports, lacking comprehensive assessment from large-scale, real-world evidence. The FDA Adverse Event Reporting System (FAERS) provides a powerful platform for post-marketing surveillance, while bibliometric analysis can elucidate evolving research landscapes 6 . This study integrates FAERS data mining with bibliometric analysis to systematically characterize the safety profile of protamine, aiming to confirm known risks, identify novel signals, and inform clinical practice. Materials and methods 2.1 Data sources and process Data on protamine as the target drug were collected from Q1 2004 to Q4 2024. Using the OpenVigil 2.1 tool, ”protamine” was searched in the FAERS database to find adverse event records where it was the Primary Suspect drug. Data extraction and cleaning were done with R software (version 4.4.2). Adverse event terms were standardized using Preferred Terms from MedDRA version 27.1 and categorized by System Organ Class (SOC). This study’s bibliometric analyses were derived from the Web of Science Core Collection (WoSCC) database, encompassing the years 1991 to 2025, focusing on relevant English articles and reviews regarding the adverse reactions of protamine. Data analysis was performed using GraphPad Prism (version 8.0.2), while scientific knowledge maps were generated and visualized with CiteSpace (version 6.2.4 R) and VOSviewer (version 1.6.18). Figure 1 presents the flowchart for the mining of FAERS data and the retrieval of literature concerning protamine-associated ADEs. 2.2 Data Analysis This study utilized a combination of four disproportionality analysis methods for adverse event signal detection and mining: the Reporting Odds Ratio (ROR), the Proportional Reporting Ratio (PRR), the Bayesian Confidence Propagation Neural Network (BCPNN), and the Muti-item Gamma Poisson Shrinker (MGPS). All calculations were based on the four-fold contingency table ( Supplementary Table 1 ). The calculation formulas and threshold criteria for these methods are summarized in Supplementary Table 2 . Only when all four algorithms alerted was an undesirable event signal genuine. An increased signal indicates a stronger connection among the target drug and the adverse event. Results 3.1 Basic Characteristics of Protamine-Related Adverse Event Reports A total of 512 protamine-related reports, encompassing 1,297 individual adverse events, were analyzed. The reports predominantly involved male patients (49.02%) and individuals aged 65 or older (41.02%), with most originating from the United States (89.84%). The vast majority of cases were serious (81.05%), and nearly all events (98.97%) occurred within 30 days after administration [Median (Q1, Q3) = 0.00 (0.00, 0.00) days]. The most frequent outcomes were life-threatening events (36.91%) and death (13.28%). Figure 2 shows all ADE categories and related SOC and PT distributions. Supplementary Figure 1 displays the ADE time-to-onset profile. Table 1 contains a complete demographic summary of these patients. 3.2 System Organ Classes and High-Risk ADE Signals Associated with Protamine Protamine-related ADEs were identified and categorized into 12 SOCs using the ROR, PRR, BCPNN, and MGPS algorithms, as detailed in Supplementary Table 3 . Cardiac disorders represented the most commonly affected system of classification (25.86%, n = 15), followed by Investigations (17.24%, n = 10) and Vascular disorders (12.07%, n = 7). At the PT level, 58 significant signals were robustly identified across all four algorithms. The strongest signals were led by procedural hypotension (ROR = 750.35), increased pulmonary artery pressure (ROR = 286.55), right ventricular dysfunction (ROR = 141.03), ventricular dilatation (ROR = 122.97), pulseless electrical activity (ROR = 116.60) (Figure 3A, B) . Cardiovascular system constituted the most affected system. Hypotension was the most commonly reported event (n = 181), exhibiting a ROR of 49.69 (95% CI: 42.47–58.18). Additional notable signals comprised elevated pulmonary arterial pressure [ROR = 286.55 (95% CI: 153.49–534.94)], and right ventricular dysfunction [ROR = 141.03 (95% CI: 45.34–438.66)]( Table 2) . Respiratory disorders were characterized by significant signals for pulmonary hypertension [ROR = 72.60 (95% CI: 51.10–103.14)] and bronchospasm [ROR = 69.56 (95% CI: 45.18–107.10)] ( Supplementary Table 4 ). Immune system disorders showed the strongest associations with anaphylactic shock [ROR = 91.51 (95% CI: 45.63–183.52)] and anaphylactic reaction [ROR = 59.86 (95% CI: 46.46–77.12)] ( Supplementary Table 5 ). Procedure-related complications revealed extremely high risks for procedural hypotension [ROR = 750.35 (95% CI: 441.13–1276.32)] and post-procedural haemorrhage [ROR = 130.82 (95% CI: 92.06–185.89)] ( Supplementary Table 6 ), indicating a heightened risk of postoperative hypotension and bleeding. Notably, we identified significant signals for events not described in the prescribing information, including resuscitation [ROR = 82.90 (95% CI: 26.67–257.67)], heparin-induced thrombocytopenia [ROR = 28.22 (95% CI: 9.09–87.65)], and acidosis [ROR = 24.62 (95% CI: 9.22–65.72)].Interestingly, enhanced therapeutic product effect [ROR = 41.30 (95% CI: 15.47–110.26)] and decreased therapeutic product effect [ROR = 19.02 (95% CI: 13.83–26.16)] showed two opposing signals ( Supplementary Table 7,8). Stratified analysis by gender indicated that procedural hypotension produced significantly high signals in both male [ROR = 1025.74 (95% CI: 422.17–2492.22)] and female [ROR = 784.99 (95% CI: 402.98–1529.16)] patients. Age-stratified analysis indicated that pulmonary hypertension exhibited the most significant association in patients under 18 years [ROR = 185.20 (95% CI: 65.99–519.73)], whereas allergic coronary spasm syndrome demonstrated the highest association in the 18–44 age group [ROR = 699.72 (95% CI: 219.53–2230.33)]. In the age groups of 45–64 and ≥65, procedural hypotension was identified as the most significant indicator, with ROR values of 866.71 and 653.84, respectively ( Supplementary Figure 2 ). 3.3 Bibliometric Analysis A review of 170 publications on protamine adverse reactions from WoSCC included 150 articles and 20 reviews, spanning 42 countries, 483 institutions, and 1,029 authors. Publications increased steadily from 1991, peaking in 2009, before slowing down ( Figure 4A ). The United States, Germany, and China were key contributors, with the U.S. leading in publication count, citations, and centrality (0.39) ( Figure 4B ). Strong international collaborations were noted, particularly between the U.S. and Germany, Denmark, Australia, and the UK, while Germany frequently collaborated with Japan, Canada, and China. Internal collaboration was more common than international partnerships. A VOSviewer term co-occurrence analysis highlighted ”protamine” as the most frequent term, followed by ”NPH insulin”, ”therapy”, ”heparin” and ”safety” (Figure 4C) . Keyword analysis identified five main research themes on protamine adverse reactions: insulin-related issues, molecular mechanisms, cardiovascular surgery, and allergic and cardiovascular complications (Supplementary Table 9, Figure 4C) . Co-citation analysis showed research evolution from fundamental mechanisms in the 1990s to clinical studies in the mid-2000s, and recent focus on drug utilization and efficacy comparison in the 2010s onward. The principal study subjects were nph insulin and heparin, with additional research on catheter ablation and teenagers (Figure 4D) . We analyzed the top 50 keywords with significant citation bursts and the 50 most cited references (Supplementary Figure 3) . Burst detection highlighted emerging research areas, including ”glargine”, ”heparin”, ”acrylamide”, ”catheter ablation”, ”adolescents”, ”ciraparantag” (a new reversal agent), and ”germline infection”. Discussion 4.1 General Characteristics of Protamine-Related Adverse Events Our analysis of 512 protamine-related adverse drug events across 27 SOCs uncovers a wider range of reactions than previously known. Cardiac, investigation, and vascular disorders are most common, reflecting the drug’s pharmacological effects and main use. More reports involved males (49.02%) than females (23.83%), possibly due to higher cardiovascular disease rates, NPH insulin use, and vasectomy history in men 7.8 . Most cases were in patients aged ≥65 (41.02%), likely due to age-related health decline and comorbidities. Reports were mainly from healthcare professionals (Pharmacists: 75.59%; Others: 14.26%), boosting credibility. Regarding onset, ADEs occurred immediately upon administration, consistent with previous studies 4 . 4.2 Cardiovascular Disorders Protamine-related ADEs mainly affect the cardiovascular system, typically causing transient hypotension, anaphylactoid reactions, and severe pulmonary vasoconstriction 9 . We identified four cardiovascular adverse event phenotypes: vasodilatory response, myocardial depression, proarrhythmic response, and pulmonary vasoconstriction (Supplementary Table 10) , which often present together in patients. Hypotension [ROR = 49.69 (95% CI: 42.47–58.18)], consistent with the drug label, was the most frequently reported event (n=181). Bibliometric analysis links hemodynamic instability after protamine use during cardiopulmonary bypass to higher in-hospital mortality, supported by a highly cited study. Welsby et al. 10 established a correlation between protamine-induced hemodynamic changes and mortality post-coronary artery bypass graft surgery. Protamine-induced hypotension may involve endothelium-dependent vasodilation via NOS activation 11 , non-immunologic histamine release 12 , active complement pathway 13 , bradykinin degradation inhibition 14 and direct effects of its positive charge on endothelial and myocardial cells 15 .Consequently, targeted management strategies can be considered. Accordingly, the following strategies can be adopted: methylene blue, ATP-sensitive K⁺ channel blockers, NF-κB inhibitors, indigo carmine, and hyperbaric oxygen therapy 16 . Our study also found a strong correlation with procedural hypotension (ROR = 750.35), highlighting the importance of blood pressure management. Furthermore, slow infusion through suitable routes may decrease the occurrence of hypotension 3 . Protamine-induced cardiotoxicity represents a core manifestation of its severe ADEs, with a clear electrophysiological and hemodynamic basis. It primarily involves direct myocardial suppression and interference with normal electrical conduction, characterized by ECG findings such as ST-segment elevation and QRS complex prolongation, potentially progressing to non-sustained ventricular tachycardia or fibrillation 17 .Clinical case reports confirm its severity. Oda Y et al. 18 a case of sinus bradycardia unresponsive to atropine 20 minutes after protamine infusion. The pathophysiological mechanisms may operate at three levels:Direct myocardial depression; Electrophysiological interference;Hemodynamic cascade 19 . However, protamine-induced bradycardia and cardiac arrest and their variable association with ventricular arrhythmias are likely multifactorial, involving susceptibility, administration methods, and pre-existing cardiac conditions. 4.3 Respiratory Disorders Protamine-induced pulmonary hypertension and bronchospasm represent critical respiratory ADEs in anesthesia and cardiovascular surgery, often occurring concomitantly. Severe pulmonary vasoconstriction typically occurs 4-10 minutes post-administration, characterized by sudden hypotension, rising pulmonary artery pressure, and decreased arterial oxygen partial pressure 2.3 . Regarding pathophysiology, thromboxane A2 is a key mediator in acute pulmonary hypertension, with complement activation, platelet activation, and neutrophil involvement accelerating this process 20 . Inhaled nitric oxide effectively antagonizes protamine-induced pulmonary vasoconstriction, as demonstrated by its successful reversal of severe pulmonary hypertension during totally endoscopic cardiac surgery 21 . Epoprostenol, a selective pulmonary vasodilator, also shows therapeutic potential 22 . In contrast, bronchospasm is primarily mediated via the leukotriene pathway, requiring a different management approach involving nebulized β2-agonists and systemic corticosteroids, highlighting the necessity for mechanism-driven, differentiated treatment 23 . 4.4 Immune System Disorders Protamine-induced anaphylaxis is a rare but severe and potentially fatal complication. Our study detected strong signals for anaphylactic shock [ROR = 91.51 (95% CI: 45.63–183.52)] and anaphylactic reaction [ROR = 59.86 (95% CI: 46.46–77.12)], which align perfectly with the ”allergy” and ”anaphylaxis” clusters in the bibliometric keyword analysis, confirming significant clinical relevance. We identified 96 allergic cases, including 63 severe reactions and 10 anaphylactic shocks. Research highlights the immunogenicity of nph insulin, linked to protamine, which raises anti-protamine IgG/IgE levels and hypersensitivity risk, unlike other insulins 24 . Affected individuals show increased susceptibility to symptoms like dyspnea, flushing, chest pain, and respiratory arrest 7 . Preoperative insulin use histories are essential for diabetic patients, especially those undergoing cardiovascular surgery. Additional risk factors comprise a history of vasectomy in males and fish allergy 8 . Recent evidence concludes that protamine is no longer contraindicated for heparin reversal based solely on a history of fish allergy 25 . For patients at high risk of protamine allergy, preoperative skin testing and serum-specific IgE measurement are recommended, with tryptase and plasma histamine assays providing additional diagnostic value 26 . In cases of allergic reactions, prompt and thorough management is essential, involving aggressive fluid resuscitation, α-adrenergic agonists for blood pressure maintenance, intravenous corticosteroids, and adrenaline. 4.5 Procedure-Related Complications The risk of post-procedural hemorrhage [ROR = 130.82 (95% CI: 92.06–185.89)] needs careful attention. Bleeding after protamine is due to overdose, causing coagulopathy, or under-dosing, leaving heparin active. Excess protamine is a more preventable risk, with ratios (0.5:1) also cause issues 27.28 . The optimal ratio (0.6–1.0) is unclear and should be tailored individually. Different situations require specific dosing strategies to reduce bleeding risk. In non-surgical patients, protamine is usually withheld. For intracranial hemorrhage, it’s used at 1 mg/100 units heparin (max 50 mg), with adjustments based on aPTT 29 . In cardiac surgery, pharmacokinetic or point-of-care protocols are preferred over empirical 1:1 dosing to avoid overdose and enhance hemostatic control 30.31 . Heparin rebound, caused by pharmacokinetic differences and tissue release of heparin, raises the risk of postoperative bleeding, especially after off-pump coronary artery bypass grafting 5 . Although a normalized ACT suggests heparin neutralization, it fails to detect low heparin levels during rebound. Administering a postoperative protamine infusion (e.g., 25 mg/h for 4-6 hours) can nearly eliminate heparin rebound. However, due to the complex causes of postoperative bleeding, blindly giving extra protamine boluses might worsen coagulopathy 32 . 4.6 Novelly Identified Suspected Adverse Events This study found significant ADEs for protamine not mentioned in its prescribing information, highlighting crucial clinical implications. FAERS data revealed strong signals for both increased and decreased therapeutic effects, indicating protamine’s dual pharmacological nature. The ”increased effect” relates to excessive anticoagulation when doses are too high or in sensitive patients, risking over-reversal and prothrombotic states 33 . The ”decreased effect” may arise from protamine’s intrinsic anticoagulant activity at high doses, insufficient heparin neutralization, or heparin rebound, which can restore anticoagulant activity and increase delayed bleeding risk 32 . Heparin-induced thrombocytopenia, a serious complication of high-dose heparin therapy, has been linked to protamine administration through data mining 34 . IgG antibodies against heparin-modified PF4 can activate blood cells via Fcγ receptor IIa (FcγRIIA) cross-linking. 35 Protamine/heparin complexes are highly immunogenic, with anti-protamine/heparin antibodies also activating platelets through FcγRIIA 36 . These complications often arise sooner than traditional HIT, particularly after cardiac surgery 37 . While clinical data may be confounded by polypharmacy and complex procedures, recent animal studies indicate that protamine alone exerts short-term antiplatelet effects in rodents—an effect attenuated by unfractionated heparin without inducing thrombocytopenia. 38 Unresponsive to stimuli had a substantial signal [ROR = 9.20 (95% CI: 3.82–22.15)], but our data could not identify any particular instances. Cytotoxicity, mitochondrial malfunction, and systemic impairment may cause most protamine-related neurological symptoms. 19 This signal needs clinical attention and verification. 5 Clinical trials of Protamine Alternatives Emerging bibliometric evidence and FAERS high-risk signals suggest that next-generation heparin reversal agents could surpass protamine’s safety limitations. This is being actively explored, with six clinical trials for alternatives like ciraparantag and Andexanet Alfa registered in the WHO ICTRP by October 25, 2025 （Table 3) . The development pipeline includes preclinical candidates such as UHRA, PyA-γ-CD, and cationic liposomes. While hexadimethrine, heparinase, and VLPs show promise, safety concerns limit their clinical use 2.3.39.40 . Transitioning from protamine to synthetic alternatives is expected to enhance patient safety, reduce adverse reactions, and improve clinical adaptability. 6 Limitations This study is constrained by the FAERS database, a spontaneous reporting system prone to underreporting, incomplete, and biased data. Even after thorough data cleaning, some reports lacked clinical details. Most reports originated from the US, potentially introducing geographical bias and limiting generalizability. FAERS is primarily useful for identifying safety signals, not for quantifying epidemiological risk or establishing causality. 7 Conclusion By integrating large-scale pharmacovigilance with bibliometric analysis, this study solidifies the understanding of protamine’s adverse event profile. We not only confirm well-documented risks like hypotension and anaphylaxis but also uncover previously underappreciated signals, including HIT,altered therapeutic effects and unresponsive to stimuli. These findings advocate for enhanced preoperative risk stratification, the adoption of individualized dosing strategies guided by real-time monitoring, and continued research into safer reversal agents. Ultimately, a more nuanced approach to protamine management is essential to improve patient safety in cardiac and vascular surgery. 7 References 1. Balhorn R. The protamine family of sperm nuclear proteins. Genome Biol. 2007;8(9):227. doi:10.1186/gb-2007-8-9-227 2. Levy JH, Ghadimi K, Kizhakkedathu JN, Iba T. What’s fishy about protamine? Clinical use, adverse reactions, and potential alternatives. J Thromb Haemost. 2023;21(7):1714-1723. doi:10.1016/j.jtha.2023.04.005 3. Boer C, Meesters MI, Veerhoek D, Vonk ABA. Anticoagulant and side-effects of protamine in cardiac surgery: a narrative review. Br J Anaesth. 2018;120(5):914-927.doi:10.1016/j.bja.2018.01.023 4. Facchetti N, Hinrichs JB, Becker LS, et al. Heparin reversal with protamine sulfate after Percutaneous Hepatic Perfusion (PHP): is less more?. Cancer Imaging. 2023;23(1):68.doi:10.1186/s40644-023-00590-7 5. Jiang F, Xu Y, Hu SS, Wang JQ, Yao YT; Evidence in Cardiovascular Anesthesia (EICA) Group. Heparin rebound in patients undergoing off-pump coronary artery bypass grafting surgery: a single-center retrospective study. J Cardiothorac Surg. 2025;20(1):18.doi:10.1186/s13019-024-03267-9 6. Shi Y, Yang Y, Liu R, et al. A Drug Similarity-Based Bayesian Method for Early Adverse Drug Event Detection. Drug Saf. 2025;48(8):923-931.doi:10.1007/s40264-025-01545-6 7. Brunetti VC, Yu OHY, Platt RW, Filion KB. The association of long-acting insulin analogue use versus neutral protamine Hagedorn insulin use and the risk of major adverse cardiovascular events among individuals with type 2 diabetes: A population-based cohort study. Diabetes Obes Metab. 2022;24(11):2169-2181.doi:10.1161/ CIRCULATIONAHA. 121.056025I 8. Adourian U, Shampaine EL, Hirshman CA,et al. High-titer protamine-specific IgG antibody associated with anaphylaxis: report of a case and quantitative analysis of antibody in vasectomized men. Anesthesiology. 1993;78(2):368-372.doi:10.1097/00000542-199302000-00024 9. Horrow JC. Protamine: a review of its toxicity. Anesth Analg. 1985;64(3):348-361. 10. Welsby IJ, Newman MF, Phillips-Bute B,et al.Hemodynamic changes after protamine administration: association with mortality after coronary artery bypass surgery. Anesthesiology. 2005;102(2):308-314doi:10.1097/00000542- 200502000 -00011. 11. Pearson PJ, Evora PR, Ayrancioglu K, Schaff HV. Protamine releases endothelium-derived relaxing factor from systemic arteries. A possible mechanism of hypotension during heparin neutralization. Circulation. 1992;86(1):289-294.doi:10.1161/01.cir.86.1.289 12. Suksompong S, Wongsripuemtet P, Srinoulprasert Y,et al.H1 and H2 antihistamines pretreatment for attenuation of protamine reactions after cardiopulmonary bypass: a randomized-controlled study. Ann Palliat Med. 2023;12(1):47-59.doi:10.21037/apm-22-714 13. Hobbhahn J, Conzen PF, Habazettl H,et al.Heparin reversal by protamine in humans–complement, prostaglandins, blood cells, and hemodynamics. J Appl Physiol (1985). 1991;71(4):1415-1421. 14. Pretorius M, Scholl FG, McFarlane JA,et al.A pilot study indicating that bradykinin B2 receptor antagonism attenuates protamine-related hypotension after cardiopulmonary bypass. Clin Pharmacol Ther. 2005;78(5):477-485.doi:10.1016/j.clpt.2005.08.010 15. Pugsley MK, Authier S, Curtis MJ. Charge is an important determinant of hemodynamic and adverse cardiovascular effects of cationic drugs. Pharmacol Res. 2015;102:46-52.doi:10.1016/j.phrs.2015.09.008 16. Liu H, Yu L, Yang L, Green MS. Vasoplegic syndrome: An update on perioperative considerations. J Clin Anesth. 2017;40:63-71.doi:10.1016/j.jclinane.2017.04.017 17. Canpolat U. Aware of the evils of life-saving antidote of heparin: clues from 12-lead electrocardiogram during protamine-mediated adverse events. Europace. 2019;21(6):991.doi:10.1093/europace/euz035 18. Oda Y, Yamasaki H, Osawa T,et al. Rescuing Protamine Anaphylaxis Refractory to Adrenaline Using Extracorporeal Membrane Oxygenation. JACC Case Rep. 2025;30(6 Pt 1):102966. doi:10.1016/j.jaccas.2024.102966 19. Miklosz J, Kalaska B, Podlasz P, et al. Cardiovascular and Respiratory Toxicity of Protamine Sulfate in Zebrafish and Rodent Models. Pharmaceutics. 2021;13(3):359.doi:10.3390/pharmaceutics13030359 20. Morel DR, Zapol WM, Thomas SJ, et al. C5a and thromboxane generation associated with pulmonary vaso- and broncho-constriction during protamine reversal of heparin. Anesthesiology. 1987;66(5):597-604. doi:10.1097/00000542-198705000-00002 21. Takeichi T, Morimoto Y, Yamada A, Tanaka T. A case of the effective inhalation of nitric oxide therapy for causing severe pulmonary hypertension with protamine neutralization of systemic heparinization during totally endoscopic minimally invasive cardiac surgery. J Extra Corpor Technol. 2024;56(3):120-124.doi:10.1051/ject/2024018 22. Guan Z, Shen X, Zhang YJ, et al. Use of epoprostenol to treat severe pulmonary vasoconstriction induced by protamine in cardiac surgery. Medicine (Baltimore). 2018;97(28):e10908.doi:10.1097/MD.0000000000010908 23. Norawat R, Vohra A, Parkes A, et al. Incidence and outcome of anaphylaxis in cardiac surgical patients. Ann Card Anaesth. 2022;25(3):323-329.doi:10.4103/aca.aca_170_21 24. Weiss ME, Nyhan D, Peng ZK, et al. Association of protamine IgE and IgG antibodies with life-threatening reactions to intravenous protamine. N Engl J Med. 1989;320(14):886-892.doi:10.1056/NEJM198904063201402 25. Youssef MR, Martinez E, Pinnock TM, et al.Assessment of Perioperative Protamine Reactions in Patients With Fish Allergies: A Retrospective Observational Study. J Cardiothorac Vasc Anesth. 2024;38(12):2925-2931. doi:10.1053/j.jvca.2024.08.024 26. Takenoshita M, Sugiyama M, Okuno Y, et al.Anaphylactoid reaction to protamine confirmed by plasma tryptase in a diabetic patient during open heart surgery. Anesthesiology. 1996;84(1):233-235.doi:10.1097/00000542-199601000-00030 27. 2024 EACTS/EACTAIC/EBCP Guidelines on cardiopulmonary bypass in adult cardiac surgery. Eur J Cardiothorac Surg. 2025;67(2):ezae354.doi:10.1093/ejcts/ezae354 28. Kneizeh K, Milzi A, Vogt F, et al. Efficacy and Safety of Low-Dose Protamine in Reducing Bleeding Complications during TAVI: A Propensity-Matched Comparison. J Clin Med. 2023;12(13):4243.doi:10.3390/jcm12134243 29. Frontera JA, Lewin JJ 3rd, Rabinstein AA, et al. Guideline for Reversal of Antithrombotics in Intracranial Hemorrhage: Executive Summary. A Statement for Healthcare Professionals From the Neurocritical Care Society and the Society of Critical Care Medicine. Crit Care Med. 2016;44(12):2251-2257.doi:10.1097/CCM.0000000000002057 30. Moilanen J, Pada M, Ohtonen P, et al. Thromboelastometry and two activated clotting tests in detecting residual heparin after protamine in cardiac surgical patients: A prospective cohort study. Eur J Anaesthesiol. 2025;42(5):398-406. doi:10.1097/EJA.0000000000002122 31. van Haeren MMT, Breel JS, Schenk J, et al. Comparison of ROTEM® Delta and ROTEM® Sigma transfusion algorithm performance in thoracic aortic surgery: a single-centre prospective observational cohort study. Br J Anaesth. 2025;134(2):317-327.doi:10.1016/j.bja.2024.09.028 32. Teoh KH, Young E, Blackall MH, et al. Can extra protamine eliminate heparin rebound following cardiopulmonary bypass surgery?. J Thorac Cardiovasc Surg. 2004;128(2):211-219.doi:10.1016/j.jtcvs.2003.12.023 33. Ni Ainle F, Preston RJ, Jenkins PV, et al. Protamine sulfate down-regulates thrombin generation by inhibiting factor V activation. Blood. 2009;114(8):1658-1665.doi:10.1182/blood-2009-05 -222109 34. Grieshaber P, Bakchoul T, Wilhelm J, et al. Platelet-activating protamine-heparin-antibodies lead to higher protamine demand in patients undergoing cardiac surgery. J Thorac Cardiovasc Surg. 2015;150(4):967-73.e1.doi:10.1016/j.jtcvs.2015.07.057 35. Rollin J, Pouplard C, Gruel Y. Risk factors for heparin-induced thrombocytopenia: Focus on Fcγ receptors. Thromb Haemost. 2016;116(5):799-805.doi:10.1160/TH16-02-0109 36. Bakchoul T, Zöllner H, Amiral J, et al. Anti-protamine-heparin antibodies: incidence, clinical relevance, and pathogenesis. Blood. 2013;121(15):2821-2827.doi:10.1182/blood-2012-10-460691 37. Bakchoul T, Jouni R, Warkentin TE. Protamine (heparin)-induced thrombocytopenia: a review of the serological and clinical features associated with anti-protamine/heparin antibodies. J Thromb Haemost. 2016;14(9):1685-1695.doi:10.1111/jth.13405 38. Miklosz J, Kalaska B, Kaminski K, et al. The Inhibitory Effect of Protamine on Platelets is Attenuated by Heparin without Inducing Thrombocytopenia in Rodents. Mar Drugs. 2019;17(9):539.doi:10.3390/md17090539 39. An WJ, Lei Z, Yu XY, et al. Polycationic γ-Cyclodextrin with Amino Side Chains for a Highly Efficient Anti-Heparin Coagulant. Adv Healthc Mater. 2025;14(26):e2404357.doi:10.1002/adhm.202404357 40. Du J, Liu Y, Dong Z, et al. Cationic liposomes as broad-spectrum antidotes for heparin-based anticoagulants. Acta Biomater. 2025;195:283-296.doi:10.1016/j.actbio.2025.02.037 FIGURE 1 The flowchart of the data analysis FIGURE 2 Proportion of adverse events associated with protamine distribution: (A) Proportion of adverse events categorized by SOC (B) Proportion of adverse events categorized by PT FIGURE 3 Adverse events of protamine involving SOC and high-risk ADE signals.(A) Venn diagrams under four different algorithms.(B) ROR values and signal strength of high-risk PTs associated with protamine-related ADEs FIGURE 4 Bibliometric analysis:(A) Annual Publication Trend on Protamine Adverse Reactions (1991-2025)(B) Geographical Distribution and International Collaboration Network(C) Co-occurrence Network and Knowledge Clusters of Research Keywords(D) Thematic Shift of Research Fronts from Fundamental Science to Clinical Practice. TABLE 1 Presents fundamental data regarding adverse event signals associated with protamine Characteristics Case number (n) Case proportion(%) Number of events 512 Gender Female 122 23.83 Male 251 49.02 Unknown 139 27.15 Age(years) <18 15 2.93 18-44 27 5.27 45-64 104 20.31 ≥65 210 41.02 Unknown 156 30.47 Reporter Pharmacist 387 75.59 Other health-professional 73 14.26 Physician 23 4.49 Not Specified 20 3.91 Consumer 7 1.37 Lawyer 2 0.39 Reported country (top five) United States of America 460 89.84 Canada 12 2.34 Austria 3 0.59 Germany 3 0.59 United Kiongdom 3 0.59 Serious Report Serious 415 81.05 Non-Serious 97 18.95 Outcomes Life-Threatening 189 36.91 Other 165 32.23 Hospitalization - Initial or Prolonged 75 14.65 Death 68 13.28 Required Intervention to Prevent Permanent Impairment/Damage 55 10.74 Disability 10 1.95 TABLE 2 Cardiovascular Reaction Signal PT PT code Events ROR ROR (95%CI Lower) ROR (95%CI Upper) Pulmonary arterial pressure increased 10037324 10 286.5464205 153.4903193 534.944819 Right ventricular dysfunction 10058597 3 141.0277086 45.33943736 438.6647862 Dilatation ventricular 10013012 6 122.9738919 55.0809615 274.5518175 Pulseless electrical activity 10058151 12 116.6035062 65.99497024 206.0214228 Haemodynamic instability 10052076 15 99.78692048 59.94539744 166.108324 Vasodilatation 10047141 5 93.87283845 38.96836047 226.1349898 Right ventricular failure 10039163 14 90.75427837 53.5665894 153.7588847 Blood pressure systolic decreased 10005758 8 84.69802899 42.23712672 169.8447946 Circulatory collapse 10009192 27 74.45433639 50.83964416 109.0379034 Electrocardiogram ST segment elevation 10014392 5 69.70867432 28.94449967 167.8833399 Kounis syndrome 10069167 3 68.08114292 21.90869599 211.561748 Pulse absent 10037469 6 57.75716308 25.88557603 128.8706066 Ventricular dysfunction 10059056 3 57.41930334 18.48028807 178.4050326 Hypotension 10021097 181 49.69269259 42.4672725 58.14745219 Bradycardia 10006093 38 34.14934195 24.72722356 47.16168611 Electrocardiogram QRS complex prolonged 10014380 3 29.52087567 9.504735522 91.68925302 Cardiac arrest 10007515 48 28.11341498 21.07046175 37.51052592 Stress cardiomyopathy 10066286 3 26.02959329 8.38104568 80.84190833 Blood pressure decreased 10005734 35 25.62149184 18.31046464 35.85167591 Ventricular fibrillation 10047290 6 25.3948099 11.38486066 56.64508234 Ventricular tachycardia 10047302 6 17.1845757 7.704682591 38.32859285 Shock 10040560 6 12.79236321 5.735674195 28.53100629 Cardio-respiratory arrest 10007617 10 10.98088259 5.893600981 20.45944115 Cardiomegaly 10007632 3 10.76784983 3.467746641 33.43571547 Cardiogenic shock 10007625 3 10.45712126 3.367691465 32.4707255 Ejection fraction decreased 10050528 3 9.128111643 2.93973863 28.34347969 Oxygen saturation decreased 10019301 6 7.956951269 3.567795366 17.74571325 Heart rate decreased 10019304 3 6.065927131 1.953630975 18.83440241 Tachycardia 10043071 9 4.838316975 2.511595498 9.320494154 Thrombosis 10043607 8 4.677004906 2.333824871 9.37275764 Haemorrhage 10055798 9 4.170403294 2.164888985 8.033790073 TABLE 3 Protamine Replacement Agents: WHO Clinical Trial Statistics Agent Main ID Public title Primary Outcome Phase Ciraparantag (PER977) NCT02206087 Evaluation of the Safety, Tolerability, Pharmacokinetics, and Pharmacodynamic Effects of PER977 Following Heparin Effect of PER977 on reversal of heparin anticoagulation [Time Frame: Single day dosing] Phase 1/Phase 2 NCT02206100 PK and PD of Single, Escalating Doses of PER977 Following Enoxaparin PER977 Number of adverse events [Time Frame: 1 day] Phase 1/Phase 2 Andexanet Alfa (Andexxa) NCT05548777 Andexanet Alfa and 4F-PCC Use in Patients Hospitalised With an Anticoagulant-related Major Bleed Mortality [Time Frame: During hospitalisation, approximately 6 days] — EUCTR2020-000374-21-AT A phase 2 clinical trial to study the effect of andexanet alfa for patients who require urgent surgery. The primary efficacy endpoint is the achievement of effective hemostasis, as determined by the surgeon’s assessment of intraoperative hemostasis and confirmed by adjudication by an independent EAC. Phase2 EUCTR2020-000374-21-DE A phase 2 clinical trial to study the effect of andexanet alfa for patients who require urgent surgery. The primary efficacy endpoint is the achievement of effective hemostasis, as determined by the surgeon’s assessment of intraoperative hemostasis and confirmed by adjudication by an independent EAC. Phase2 NCT02329327 A Study in Participants With Acute Major Bleeding to Evaluate the Ability of Andexanet Alfa to Reverse the Anticoagulation Effect of Direct and Indirect Oral Anticoagulants (Extension Study) Proportion of patients with excellent or good hemostasis [Time Frame: Stopping major bleed at 12 hours from the start of andexanet bolus] Phase 3 Supplementary Material File (pds-26-0137-file003.tif) Download 112.31 MB File (pds-26-0137-file004.tif) Download 92.56 MB File (pds-26-0137-file005.tif) Download 35.18 MB File (pds-26-0137-file007.tif) Download 82.19 MB File (pds-26-0137-file008.tif) Download 109.15 MB Information & Authors Information Version history V1 Version 1 11 February 2026 Copyright This work is licensed under a Non Exclusive No Reuse License. Keywords adverse events bibliometric analysis faers pharmacovigilance study protamine Authors Affiliations weitong wu Hebei Medical University View all articles by this author Qian Guo The First Affiliated Hospital of Zhengzhou University View all articles by this author Xiaopeng Ma Hebei Medical University View all articles by this author Tengyue Zhao [email protected] The Second Hospital of Hebei Medical University View all articles by this author Metrics & Citations Metrics Article Usage 240 views 102 downloads .FvxKWukQNSOunydq8rnd { width: 100px; } Citations Download citation weitong wu, Qian Guo, Xiaopeng Ma, et al. Adverse Reactions to Protamine: A Study Based on the FAERS Database and Bibliometric Analysis. Authorea . 11 February 2026. DOI: https://doi.org/10.22541/au.177084046.62985429/v1 If you have the appropriate software installed, you can download article citation data to the citation manager of your choice. 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