Pyrethroid poisonings with toxidrome mimicking organophosphate poisoning

Pyrethroids ore generally considered safe because of their very high mammalian safety factor and they are quickly degradable in the environment. It has been shown that nerve membrane is the most important target site of pyreihroids in invertibrate nervous system. Commonly observed clinical effects in human poisonings are tremors, hyperacitability, salivation, choreathetosis, paralysis etc. Large doses (200–500ml) of concentrated formulations may cause hypotension, tachycardia, seizures and coma. On the other hand clinical effects associated with organophospate/corbamate poisoning are altered sensorium, miosis, SLUDGE (Salivation Lacrimation, Defecation, GI distress, Emesis) Syndrome, bronchospasm, bradycardia, hypotension, convulsions, respiratory paralysis etc. Though pyrethroids and organophosphates have some common features of poisoning ‘miosis’ is not reported to he associated with pyrethroid poisioning.

At the National Poisons Information Centre (NPIC), AIIMS, New Delhi. we have come across a few cases where ‘miosis’ was a feature of pyrethroid poisoning. In the first case that was reported to our Centre, the sample that involved in thc poisoning was screened for both organophosphate and carbamate and was found to be negative. It can be difficult to distinguish between poisoning caused by pyrethroid and organophosphate exporures in the absence of a correct history. It increases he chance of incorrect diagnosis. Since pyrethroids do not inhibit cholinesterase activity, it is suggested that estimation of acetyl choline esterase levels can be used to establish crucial differential diagnosis.