Aluminum phosphide poisoning: an unsolved riddle

Aluminum phosphide (ALP), a widely used insecticide and rodenticide, is also infamous for the mortality and morbidity it causes in ALP-poisoned individuals. The toxicity of metal phosphides is due to phosphine liberated when ingested phosphides come into contact with gut fluids. ALP poisoning is lethal, having a mortality rate in excess of 70%. Circulatory failure and severe hypotension are common features of ALP poisoning and frequent cause of death. Severe poisoning also has the potential to induce multi-organ failure. The exact site or mechanism of its action has not been proved in humans. Rather than targeting a single organ to cause gross damage, ALP seems to work at the cellular level, resulting in widespread damage leading to multiorgan dysfunction (MOD) and death. There has been proof in vitro that phosphine inhibits cytochrome c oxidase. However, it is unlikely that this interaction is the primary cause of its toxicity. Mitochondria could be the possible site of maximum damage in ALP poisoning, resulting in low ATP production followed by metabolic shutdown and MOD; also, owing to impairment in electron flow, there could be free radical generation and damage, again producing MOD. Evidence of reactive oxygen species-induced toxicity owing to ALP has been observed in insects and rats. A similar mechanism could also play a role in humans and contribute to the missing link in the pathogenesis of ALP toxicity. There is no specific antidote for ALP poisoning and supportive measures are all that are currently available.