Who is the real killer? Chlorfenapyr or detergent micelle-chlorfenapyr complex?

1. Chlorfenapyr [4-bromo-2-(4-chlorophenyl)-1-(ethoxymethl)-5-(trifluoromethyl)-1H-pyrrole-3-carbonitrile] is a commonly employed pesticide throughout the world. The mechanism of chlorfenapyr action is to uncouple oxidative phosphorylation in the mitochondria. The characteristic features of chlorfenapyr intoxication are high fever, rhabdomyolysis and neurologic symptoms that gradually get worse until death. 2. In recent years, suicide attempt cases using commercial chlorfenapyr pesticide were reported. Even small doses of commercial chlorfenapyr pesticide intoxication caused human fatality. However, world health organization (WHO) has classified chlorfenapyr as class 2-moderately hazardous chemical. Animal studies using technical grade (94.5%; AC 7504-59A) chlorfenapyr in 0.5% carboxy methyl cellulose as the vehicle, single dose through oral route in male rats were well tolerated. 3. We planned a therapeutic strategy for suicidal chlorfenapyr intoxication, therefore we evaluated the three different toxic doses of chlorfenapyr (10% chlorfenapyr and 90% detergent) through oral route in male rats for human extrapolation. The major difference between the technical grade chlorfenapyr and commercial grade chlorfenapyr was the vehicle. In the technical grade chlorfenapyr study, 0.5% carboxy methyl cellulose was used as a vehicle, whereas in the present study 90% detergent acted as a vehicle. The LD50 of commercial grade chlorfenapyr-40.63 mg/kg bw, which was approximately tenfold decrease than technical grade chlorfenapyr, LD50–441 mg/kg bw. 4. The combination of chlorfenapyr and detergent, a deadly cocktail to form micelle complex that can greatly influence bioavailability by attaching to biological membranes in vivo. To conclude, the enhanced bioavailability of chlorfenapyr by the detergent causes the fatality in suicidal attempts using chlorfenapyr.