Retinoid concentrations in skin, serum and adipose tissue of patients treated with etretinate.

Synthetic and natural retinoids were analysed in epidermis, dermis, subcutis and serum of twenty-seven patients treated with etretinate (0.6-1.0 mg/kg/day) for 1-36 months. The concentrations of etretinate (including its major metabolite) in serum and normal-appearing epidermis were 150-600 ng/ml and 50-350 ng/g, respectively. The serum and epidermal values were significantly correlated (P less than 0.05). The drug progressively accumulated in the subcutis attaining a maximum value of 15,500 ng/g. After the treatment, etretinate disappeared from the epidermis within 1 week. By contrast, the drug remained in the subcutis for several months after cessation of treatment. The epidermal composition of endogenous retinoids changed during etretinate therapy as reflected in an increased ratio of 3-dehydroretinol to all-trans retinol.