Intramuscular Cobinamide As An Antidote To Methyl Mercaptan Poisoning

BackgroundMethyl 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.MethodsWe conducted a randomized trial in 12 swine comparing no treatment to intramuscular injection of the vitamin B-12 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.ResultsAll 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.ConclusionWe conclude that intramuscular administration of cobinamide improves survival and clinical outcomes in a large animal model of acute, high dose methyl mercaptan poisoning.