Cyanide Medical Countermeasure Development: Assessing the Efficacy of Intramuscular Sodium Tetrathionate for the Treatment of Acute, Severe Cyanide Toxicity in Swine (Sus scrofa)

Introduction: Given its availability and lethality, cyanide has potential for weaponization and thus has the attention of several governmental agencies. In large scale exposure scenarios, an effective countermeasure that can be administered quickly and in low volume intramuscularly may prove valuable because IV medications may have limited practical applications in these situations. Sodium tetrathionate, a potential cyanide antidote, is a compound that provides sulfur to rhodanese, the enzyme that detoxifies cyanide endogenously. Additionally, sodium tetrathionate has been reported to directly react with cyanide and is effective when administered intramuscularly. In this study, we assess the efficacy of sodium tetrathionate, when administered intramuscularly for the treatment of acute, oral cyanide poisoning in swine.

Methods: We conducted a prospective trial approved by the 59th Medical Wing Institutional Animal Care and Use Committee comparing intramuscular sodium tetrathionate (n=6) to no treatment control (n=4) in animals (Sus scrofa) exposed to a lethal dose of oral potassium cyanide. Survival at 120 minutes was the primary outcome. Lactate, a cyanide toxicity biomarker, was measured. At the study end, all animals were euthanized in compliance with the Animal Welfare Act and the American Association for Accreditation of Laboratory Animal Care. Survival between groups was summarized using a Kaplan-Meier survival curve after comparing survival by log-rank, Mantel-Cox analysis. The Mann-Whitney U test was used for comparison of other variables between groups.

Results: At baseline animals were similar. There was 100% survival in the treatment group and 0% survival in the control group (P=0.0011). Serum lactate significantly increased in the control group (control: 5±0.9 vs. treatment: 2.1 ± 0.5 mmol/L at 20 minutes).

Conclusion: Sodium tetrathionate (intramuscular) significantly improved survival in a large, swine model of acute, oral cyanide poisoning. Future studies will be directed at further assessing sodium tetrathionate as a potential medical countermeasure for cyanide poisoning.