Thiosulphate and hydroxocobalamin prophylaxis in progressive cyanide poisoning in guinea-pigs

Hydroxocobalamin in cyanide poisoning

INTRODUCTION

On theoretical grounds, hydroxocobalamin is an attractive antidote for cyanide poisoning as cobalt compounds have the ability to bind and detoxify cyanide. This paper reviews the pharmacokinetic and pharmacodynamic aspects of hydroxocobalamin, its efficacy in human cyanide poisoning and its adverse effects.

METHODS

PubMed was searched for the period 1952 to April 2012. A total of 71 papers were identified in this way; and none was excluded. PHARMACOKINETICS AND PHARMACODYNAMICS: Pharmacokinetic studies in dogs and humans suggest a two-compartment model, with first order elimination kinetics. Pharmacodynamic studies in animals suggest that hydroxocobalamin would be a satisfactory antidote for human cyanide poisoning. EFFICACY IN HUMAN POISONING: There is limited evidence that hydroxocobalamin alone is effective in severe poisoning by cyanide salts. The evidence for the efficacy of hydroxocobalamin in smoke inhalation is complicated by lack of evidence for the importance of cyanide exposure in fires and the effects of other chemicals as well as confounding effects of other therapeutic measures, including hyperbaric oxygen. Evidence that hydroxocobalamin is effective in poisoning due to hydrogen cyanide alone is lacking; extrapolation of efficacy from poisoning by ingested cyanide salts may not be valid. The rate of absorption may be greater with inhaled hydrogen cyanide and the recommended slow intravenous administration of hydroxocobalamin may severely limit its clinical effectiveness in these circumstances.

ADVERSE EFFECTS

Both animal and human data suggest that hydroxocobalamin is lacking in clinically significant adverse effects. However, in one human volunteer study, delayed but prolonged rashes were observed in one-sixth of subjects, appearing 7 to 25 days after administration of 5 g or more of hydroxocobalamin. Rare adverse effects have included dyspnoea, facial oedema, and urticaria.

CONCLUSIONS

Limited data on human poisonings with cyanide salts suggest that hydroxocobalamin is an effective antidote; data from smoke inhalation are less clear-cut. Although clinically important reactions to hydroxocobalamin have not been seen, some, non-life threatening, adverse reactions can occur.

Hydroxocobalamin: improved public health readiness for cyanide disasters

The United States is under the constant threat of a mass casualty cyanide disaster from industrial accidents, hazardous material transportation incidents, and deliberate terrorist attacks. The current readiness for cyanide disaster by the emergency medical system in the United States is abysmal. We, as a nation, are simply not prepared for a significant cyanide-related event. The standard of care for cyanide intoxication is the cyanide antidote kit, which is based on the use of nitrites to induce methemoglobinemia. This kit is both expensive and ill suited for out-of-hospital use. It also has its own inherent toxicity that prevents rapid administration. Furthermore, our hospitals frequently fail to stock this life-saving antidote or decline to stock more than one. Hydroxocobalamin is well recognized as an efficacious, safe, and easily administered cyanide antidote. Because of its extremely low adverse effect profile, it is ideal for out-of-hospital use in suspected cyanide intoxication. To effectively prepare for a cyanide disaster, the United States must investigate, adopt, manufacture, and stockpile hydroxocobalamin to prevent needless morbidity and mortality.