INSECT REPELLENT FORMULATIONS OF N,N-DIETHYL-M-TOLUAMIDE (DEET) IN A LIPOSPHERE SYSTEM - EFFICACY AND SKIN UPTAKE

Novel formulations for deet in liposphere microdispersion in the form of lotion were prepared from natural solid triglycerides and phospholi pids dispersed in buffer solution. The formulations containing 6.5, 10 , and 20% deet were effective as a repellent against the common aggres sive biting mosquitoes, Aedes aegypti and Anopheles stephensi, for up to 6 h. The acute dermal absorption of the 10% loaded formulation was conducted in rabbits using C-14-labeled deet. C-14-labeled deet, 10% i n alcohol solution or in liposphere microdispersion was applied to the intact rabbit skin under a porous nonirritating cover for 7 days. Pla sma levels of radioactivity were determined for 24 h, and daily for a total of 7 days. The C-14-deet blood levels following intravenous bolu s administration were also measured. The bioavailability of deet from 10% ethanol solution was 45%, whereas the bioavailability of deet from lipospheres was 16%, a 3-fold reduction in the amount of deet absorbe d. Examination of the rabbits during the experiment and after necropsy showed no evidence of toxicity or irritation. The 10% deet-liposphere formulation was stable at room temperature for at least 1 year.