Biosafety of Intramuscular Autoinjection of Sulfanegen, a New Cyanide Antidote, in a Porcine Model Deepali Shrivastava, Arreh Jain, Steven E. Patterson, Walt Tollison, John Carney, David Beebe, Kumar G. Belani Background: Sulfanegen is a potent antidote to severe cyanide toxicity and can be administered intramuscularly. A proprietary intramuscular autoinjector has been developed for rapid administration during emergencies. This study investigated the safety of sulfanegen administered via the autoinjector in a porcine model, focusing on its systemic biochemical and metabolic toxicity and local tissue reaction. Methods: After IACUC approval, eight healthy juvenile Yorkshire pigs (16-20 kg) were sedated with Tiletemine/Zolazepam (2-7 mg/kg) and Xylazine (0.2-1 mg/kg). Monitoring in these spontaneously breathing pigs included continuous EKG, pulse oximetry, respiratory rate, blood pressure, and temperature. Surface warming ensured normothermia. Blood samples were collected via peripheral venous blood before sulfanegen injection with a novel automatic injection system. The calculated body weight dose of Sulfanegen (75 mg/kg) was divided between two injectors and injected simultaneously into each of the hind thigh muscles. Hemodynamic parameters such as heart rate, respiratory rate, oxygen saturation, and core temperature were monitored throughout the procedure. Pre- and post-injection blood samples were collected for biochemical evaluation. After the Sulfanegen injection, the pigs recovered and observed for 7 days. They were then sedated again with the tiletamine/zolazepam and Xylazine mixture to collect metabolic blood samples and humanely euthanized for a necropsy. The muscle injection sites were grossly examined. Hemodynamic and biochemical data were analyzed using SPSS v27. Results: All the pigs survived the Sulfanegen injection. Hemodynamics and biochemical parameters remained stable during and immediately following the injection without significant changes. Following emergence from anesthesia, all pigs were active and feeding appropriately. At necropsy, the local muscle tissue at the injection sites showed only minimal inflammation and no necrosis. Liver function, hematological, and metabolic tests at necropsy were within normal range. Conclusion: In this porcine model, the intramuscular injection of Sulfanegen using the proprietary autoinjector device did not exert any adverse biochemical, hematological, or hemodynamic effects. There was only minimal local irritation at the injection sites. The next steps would be to examine the effects of increased doses of sulfanegen on muscle tissue in this model.