Biotransformation and toxicokinetics of the insect repellent IR3535? in male and female human subjects after dermal exposure

摘要

The absorption and excretion of the insect repellent IR3535? was studied in human subjects (five males and five females) after dermal application of approx. 3g of a formulation containing 20% IR3535?, i.e. the amounts of IR3535? applied were between 1.94 and 3.4mmol/person (418-731mg/person). Blood and urinary concentrations of IR3535? and its only metabolite, IR3535?-free acid, were determined over time. In plasma, concentrations of the parent compound IR3535? were at or below the limit of quantification (0.037μmol/L). IR3535?-free acid peaked in plasma samples 2-6h after dermal application. Cmax mean values were 5.7μmol/L in males, 3.0μmol/L in females and 4.2μmol/L in all volunteers. Mean AUC values were 41.6, 24.5 and 33.9μmolL-1h in males, females and all subjects, respectively. In urine samples from all human subjects, both IR3535? and IR3535?-free acid were detectable, however, only very small amounts of IR3535? were found. Concentrations of IR3535?-free acid were several thousand-fold higher than the parent compound and peaked at the first two sampling points (4h and 8h after dermal application). Overall, IR3535? and IR3535?-free acid excreted with urine over 48h representing 13.3±3.05% of the dose applied. Since IR3535? is rapidly and extensively metabolized, and IR3535?-free acid has a low molecular weight and high water solubility, it is expected that urinary excretion of IR3535?-free acid and IR3535? represents the total extent of absorption of IR3535? in humans. Based on the results of this study, the skin penetration rate of IR3535? is 13.3% in humans after dermal application.