Comparative percutaneous absorption of lindane and permethrin

Background and Design: Because of the concern for potential neurotoxic effects (central nervous system excitation, convulsions) in the treatment of scabies using 1% lindane lotion, 5% permethrin cream has been suggested as an alternative scabicide. Using the finite dose technique, in vitro percutaneous absorption of 5% permethrin cream or 1% lindane lotion was measured in human and guinea pig skin following a single application. In vivo blood and brain levels of the scabicides were measured in guinea pigs following three daily applications of 5% permethrin cream or 1% lindane lotion. Permethrin and lindane levels were quantified by gas chromatography/mass spectroscopy. Results: in vitro percutaneous absorption of the two scabicides was identical in guinea pig skin; however, human skin was 20-fold more permeable to lindane than to permethrin. In vivo guinea pig blood and brain levels of lindane were fourfold greater than permethrin levels. Conclusion: The risk for toxic effects, as assessed by systemic exposure during overuse conditions, is projected to be 40 to 400 times lower for 5% permethrin cream than for 1% lindane lotion.