Background and Design: Because of the concern for potential neurotoxic
effects (central nervous system excitation, convulsions) in the treat
ment 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% lindan
e lotion was measured in human and guinea pig skin following a single
application. In vivo blood and brain levels of the scabicides were mea
sured in guinea pigs following three daily applications of 5% permethr
in cream or 1% lindane lotion. Permethrin and lindane levels were quan
tified by gas chromatography/mass spectroscopy. Results: in vitro perc
utaneous absorption of the two scabicides was identical in guinea pig
skin; however, human skin was 20-fold more permeable to lindane than t
o permethrin. In vivo guinea pig blood and brain levels of lindane wer
e fourfold greater than permethrin levels. Conclusion: The risk for to
xic effects, as assessed by systemic exposure during overuse condition
s, is projected to be 40 to 400 times lower for 5% permethrin cream th
an for 1% lindane lotion.