Insect repellent formulations of N,N-diethyl-m-toluamide (deet) in a liposphere system: efficacy and skin uptake.

Novel formulations for a deet in liposphere microdispersion in the form of lotion were prepared from natural solid triglycerides and phospholipids dispersed in buffer solution. The formulations containing 6.5, 10, and 20% deet were effective as a repellent against the common aggressive 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 14C-labeled deet. 14C-labeled deet, 10% in alcohol solution or in liposphere microdispersion was applied to the intact rabbit skin under a porous nonirritating cover for 7 days. Plasma levels of radioactivity were determined for 24 h, and daily for a total of 7 days. The 14C-deet blood levels following intravenous bolus 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 absorbed. 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.