Intramuscular cobinamide as an antidote to methyl mercaptan poisoning

Abstract

Background

Methyl mercaptan occurs naturally in the environment and is found in a variety of occupational settings, including the oil, paper, plastics, and pesticides industries. It is a toxic gas and deaths from methyl mercaptan exposure have occurred. The Department of Homeland Security considers it a high threat chemical agent that could be used by terrorists. Unfortunately, no specific treatment exists for methyl mercaptan poisoning.

Methods

We conducted a randomized trial in 12 swine comparing no treatment to intramuscular injection of the vitamin B₁₂ analog cobinamide (2.0 mL, 12.5 mg/kg) following acute inhalation of methyl mercaptan gas. Physiological and laboratory parameters were similar in the control and cobinamide-treated groups at baseline and at the time of treatment.

Results

All six cobinamide-treated animals survived, whereas only one of six control animals lived (17% survival) (p = 0.0043). The cobinamide-treated animals returned to a normal breathing pattern by 3.8 ± 1.1 min after treatment (mean ± SD), while all but one animal in the control group had intermittent gasping, never regaining a normal breathing pattern. Blood pressure and arterial oxygen saturation returned to baseline values within 15 minutes of cobinamide-treatment. Plasma lactate concentration increased progressively until death (10.93 ± 6.02 mmol [mean ± SD]) in control animals, and decreased toward baseline (3.79 ± 2.93 mmol [mean ± SD]) by the end of the experiment in cobinamide-treated animals.

Conclusion

We conclude that intramuscular administration of cobinamide improves survival and clinical outcomes in a large animal model of acute, high dose methyl mercaptan poisoning.

Keywords:

• Methyl mercaptan
• methanethiol
• cobinamide
• inhalation
• swine

Disclosure statement

No potential conflict of interest was reported by the author(s). A patent for cobinamide has been issued, but no license or royalties.

Additional information

Funding

The present research was financially supported by National Institute of Environmental Health Sciences U54NS097214 and National Institute of Neurological Disorders and Stroke U01NS087964.