Characterization of a Swine (Sus scrofa) Model of Oral Potassium Cyanide Intoxication

A novel aqueous dimethyl trisulfide formulation is effective at low doses against cyanide toxicity in non-anesthetized mice and rats

BACKGROUND

Cyanide (CN) is a metabolic poison that is capable of intoxicating individuals through accidental or intentional means. With high concentration exposures, death can occur in minutes. In cases of mass casualty exposures, there is a need for a rapid-acting countermeasure capable of being administered in a short period of time in a pre-hospital setting to treat victims.

OBJECTIVE

These studies evaluate the safety and efficacy of a novel aqueous formulation of dimethyl trisulfide (DMTS) as an intramuscular (IM) CN countermeasure using non-anesthetized rodent models.

METHODS

Non-anesthetized rodents (mice and rats) were exposed to hydrogen cyanide (HCN) or potassium cyanide (KCN) along with immediate IM 10% DMTS treatment or vehicle treatment. Survival and other parameters, such as the time to recovery and assessment of clinical toxic signs (e.g., gasping, loss of righting reflex, convulsions, etc.), were quantified to determine the effectiveness of 10% DMTS treatment (12.5, 25, 75 mg/kg IM) compared to vehicle control treatment. A rat KCN delayed-treatment model with a 15-minute treatment delay was also utilized to simulate a real-life exposure/treatment scenario with 10% DMTS treatment. The stability of the 10% DMTS formulation was also assessed.

RESULTS

A 25 mg/kg IM dose of 10% DMTS exhibits potent efficacy against subcutaneous (SC) KCN challenge in both mice and rats and inhalational HCN exposure in mice. 10% DMTS treatment also shortens the time to recovery in rats using a delayed-treatment model.

CONCLUSION

IM treatment with 10% DMTS improves survival and clinical outcomes in non-anesthetized rodent models of acute CN toxicity. Additionally, the use of an SC KCN delayed-treatment model in rats is advised to assess the performance of a candidate CN countermeasure in a more realistic exposure/treatment scenario.

Efficacy of oral administration of sodium thiosulfate in a large, swine model of oral cyanide toxicity

INTRODUCTION

Cyanide is a deadly poison, particularly with oral exposure where larger doses can occur before symptoms develop. Prior studies and multiple governmentagencies highlight oral cyanide as an agent with the potential for use in a terrorist attack. Currently, there are no FDA approved antidotes specific to oralcyanide. An oral countermeasure that can neutralize and prevent absorption of cyanide from the GI tract after oral exposure is needed. Our objective was toevaluate the efficacy of oral sodium thiosulfate on survival and clinical outcomes in a large, swine model of severe cyanide toxicity.

METHODS

Swine (45-55kg) were instrumented, sedated, and stabilized. Potassium cyanide (8 mg/kg KCN) in saline was delivered as a one-time bolus via an orogastric tube. Three minutes after cyanide, animals randomized to the treatment group received sodium thiosulfate (510 mg/kg, 3.25 M solution) via orogastric tube. Our primary outcome was survival at 60 minutes after exposure. We compared survival between groups by log-rank, Mantel-Cox analysis and trended labs and vital signs.

RESULTS

At baseline and time of treatment all animals had similar weights, vital signs, and laboratory values. Survival at 60 min was 100% in treated animals compared to 0% in the control group (p=0.0027). Animals in the control group became apneic and subsequently died by 35.0 min (20.2,48.5) after cyanide exposure. Mean arterial pressure was significantly higher in the treatment group compared to controls (p=0.008). Blood lactate (p=0.02) and oxygen saturation (p=0.02) were also significantly different between treatment and control groups at study end.

CONCLUSION

Oral administration of sodium thiosulfate improved survival, blood pressure, respirations, and blood lactate concentrations in a large animal model of acute oral cyanide toxicity.

Efficacy of Oral Administration of Sodium Thiosulfate and Glycine in a Large, Swine Model of Oral Cyanide Toxicity

STUDY OBJECTIVE

Cyanide is a deadly poison, particularly with oral exposure, in which larger doses can occur before any symptoms develop. Multiple governmental agencies highlight oral cyanide as an agent that can be used in a terrorist attack because it can be easily weaponized and is readily available. Currently, there are no Food and Drug Administration-approved antidotes specifically for oral cyanide. An oral countermeasure that can neutralize and prevent absorption of cyanide from the gastrointestinal tract after oral exposure is needed. The objective of this study is to determine if the combination of glycine and sodium thiosulfate administered orally is effective in reducing mortality in a large, swine model of oral cyanide toxicity.

METHODS

Nine swine (45 to 55 kg) were instrumented, sedated, and stabilized. Potassium cyanide (at 8 mg/kg) in saline solution was delivered as a onetime bolus through an orogastric tube. Three minutes after cyanide administration, animals that were randomized to the treatment group received sodium thiosulfate (508.2 mg/kg, 3.25-M solution) and glycine (30 mg/kg, 3.5-M solution) through an orogastric tube. Survival at 60 minutes was the primary outcome. We compared survival between groups by log-rank Mantel-Cox analysis and trended laboratory results and vital signs.

RESULTS

At baseline and treatment, all animals were similar. Survival at 60 minutes was 100% in treated animals compared with 0% in the control group (P=.003). By the study end, defined as death or 60 minutes after cyanide administration, there was a significant difference in the lactate concentration between the treatment and control groups (control 9.43 mmol/L [SD 4.08]; treatment 1.66 mmol/L [SD 0.82]; difference between means 7.69 mmol/L [SD 2.07]; 95% confidence interval difference -14.05 to -1.32). Mean arterial pressure was significantly different between the treatment and control groups at study end (control 26 mm Hg [SD 6.7]; treatment 81 mm Hg [SD 14]; difference between means 55.2 mm Hg [SD 7.1]; 95% confidence interval difference 37.8 to 72.6). pH and oxygen saturation were also significantly different between the treatment and control groups at study end.

CONCLUSION

The combination of oral sodium thiosulfate and glycine significantly improved survival and physiologic parameters in a large-animal model of oral cyanide toxicity.

A Review on Ingested Cyanide: Risks, Clinical Presentation, Diagnostics, and Treatment Challenges

Cyanide, a metabolic poison, is a rising chemial threat and ingestion is the most common route of exposure. Terrorist organizations have threatened to attack the USA and international food and water supplies. The toxicokinetics and toxicodynamics of oral cyanide are unique, resulting in high-dose exposures, severe symptoms, and slower onset of symptoms. There are no FDA-approved therapies tested for oral cyanide ingestions and no approved intramuscular or oral therapies, which would be valuable in mass casualty settings. The aim of this review is to evaluate the risks of oral cyanide and its unique toxicokinetics, as well as address the lack of available rapid diagnostics and treatments for mass casualty events. We will also review current strategies for developing new therapies. A review of the literature using the PRISMA checklist detected 7284 articles, screened 1091, and included 59 articles or other reports. Articles referenced in this review were specific to risk, clinical presentation, diagnostics, current treatments, and developing therapies. Current diagnostics of cyanide exposure can take hours or days, which can delay treatment. Moreover, current therapies for cyanide poisoning are administered intravenously and are not specifically tested for oral exposures, which can result in higher cyanide doses and unique toxicodynamics. New therapies developed for oral cyanide exposures that are easily delivered, safe, and can be administered quickly by first responders in a mass casualty event are needed. Current research is aimed at identifying an antidote that is safe, effective, easy to administer, and has a rapid onset of action.