Topical application of a chlordane-containing ectoparasiticide: effect on the plasma half-life of warfarin in dogs.

Brief exposure of dogs to topical chlordane solutions resulted in a significant and long-lasting decrease in the biological half-life of orally administered warfarin. The effect is presumed to be an expression of chlordane's well-documented inductive effect on hepatic microsomal drug metabolizing enzymes and its long-term storage in fat depots. The facility with which chlordane is absorbed through the intact skin of dogs may render casually-treated animals unsuitable for subsequent pharmacologic study for long periods of time.