Role of hydroxocobalamin in acute cyanide poisoning

To review the recently approved cyanide antidote, hydroxocobalamin, and describe its role in therapy.

Relevant publications were identified through a systematic search of PubMed using the MeSH terms and key words hydroxocobalamin and cyanide. This search was then limited to human studies published since 2000. Systematic searches were conducted through January 2008. References from identified articles were reviewed for additional pertinent human studies.

The literature search retrieved 7 studies on the safety and/or efficacy of hydroxocobalamin in humans. Four new studies were identified by the search and 3 studies were identified from the references.

Studies of antidote efficacy in humans are ethically and logistically difficult. A preclinical study demonstrated that intravenous doses of hydroxocobalamin 5 g are well tolerated by volunteer subjects. Hydroxocobalamin has been shown to reduce cyanide concentrations in controlled studies of nitroprusside therapy and in heavy smokers. A retrospective study of 14 acute cyanide poisonings also demonstrated hydroxocobalamin's safety and efficacy. Two studies examining hydroxocobalamin for smoke inhalation-associated cyanide poisoning indicated a possible benefit, but they are insufficient to establish definitive criteria for use in this setting. Randomized controlled trials of hydroxocobalamin and traditional cyanide antidotes (nitrites/thiosulfate) are lacking.

Cyanide poisoning can rapidly cause death. Having an effective antidote readily available is essential for facilities that provide emergency care. In cases of cyanide ingestion, both the nitrite/thiosulfate combination and hydroxocobalamin are effective antidotes. Hydroxocobalamin offers an improved safety profile for children and pregnant women. Hydroxocobalamin also appears to have a better safety profile in the setting of cyanide poisoning in conjunction with smoke inhalation. However, current data are insufficient to recommend the empiric administration of hydroxocobalamin to all victims of smoke inhalation.