Pharmacokinetics of doxepin in subjects with pruritic atopic dermatitis.

Background: Doxepin applied topically by itself or in combination with triamcinolone acetonide is a safe and effective treatment for atopic dermatitis.
Objective: We evaluated the pharmacokinetic profile of doxepin and desmethyldoxepin after topical application of doxepin hydrochloride 5% cream alone or in combination with 0.025% triamcinolone acetonide (doxepin/TAC).
Methods: Twenty-four subjects with atopic dermatitis received either doxepin or doxepin/TAC cream 4 times daily for 7 days in a randomized, double-blind, controlled trial. Serum samples were obtained and pharmacokinetic parameters estimated from the dose-normalized serum concentrations of doxepin and desmethyldoxepin. Efficacy and adverse experiences were determined by physician and subject evaluations.
Results: Pharmacokinetic parameters (K(e ), t(1/2 ) and AUC) calculated in 9 subjects (doxepin/TAC = 4 subjects, doxepin = 5 subjects) with detectable serum concentrations were similar for both groups. Pruritus relief and lessening of pruritus severity were significantly greater with doxepin/TAC than doxepin alone.
Conclusion: Topically applied doxepin is safe and effective therapy for pruritus.