Penetration and Metabolism of trans-Cypermethrin in a Susceptible and a Pyrethroid-Resistant Strain of Helicoverpa armigera

The pharmacokinetics of [14C]trans-cypermethrin was studied to illustrate the differences in penetration and metabolism between a susceptible and a resistant Thailand strain of Helicoverpa armigera (Hübner). The resistant strain was found to possess a mechanism of reduced cuticular penetration to trans-cypermethrin. However, the metabolism studies did not provide sufficient evidence of an enhanced rate of metabolism in the resistant strain. The major extractable components of feces of both the susceptible and the resistant strains were trans3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylic acid and highly polar metabolites.