Use of vitamin B12 in the treatment and prevention of nitroprusside-induced cyanide toxicity.

OBJECTIVE: To review the mechanism of action, safety, and efficacy of hydroxocobalamin in the treatment and prevention of nitroprusside-induced cyanide toxicity. DATA SOURCES: English and foreign-language journal articles and reference texts identified from Index Medicus. Both animal and human studies were included. DATA SYNTHESIS: High-dose or prolonged therapy with nitroprusside in patients with hepatic or renal dysfunction increases the risk for nitroprusside-induced cyanide or thiocyanate toxicity, respectively. Hydroxocobalamin has been shown to significantly reduce RBC and plasma cyanide concentrations in animals and surgical patients without producing clinically important adverse effects or toxic metabolites. Thiosulfate infusions also decrease cyanide toxicity but can cause accumulation of thiocyanate resulting in clinical toxicity. Cyanocobalamin cannot effectively remove cyanide due to poor binding.
CONCLUSIONS: Hydroxocobalamin is a safe and effective agent in the prevention and treatment of nitroprusside-induced cyanide toxicity. Prolonged or high-dose infusions of nitroprusside should be minimized in critically ill patients, especially if hepatic and/or renal dysfunction is present.