Psoralen pharmacology: studies on metabolism and enzyme induction

Psoralens, tricyclic furocoumarins with potent photosensitizing properties in the skin, are now widely used in the treatment of several dermatologic diseases. In this study, the metabolism of 4,5',8-trimethylpsoralen (TMP) and 8-methoxypsoralen (8-MOP) was studied in mouse liver. Orally administered TMP is transformed into several metabolites, the major one of which is 4,8-dimethyl-5'-carboxypsoralen (DMCP) in both humans and mice. Orally administered 8-MOP is metabolized into at least 5 fluorescent moieties, including 8-hydroxypsoralen, the 4'5'-dihydro-diol of 8-MOP, and furocoumaric acid. The effects of 3 psoralens, 8-MOP, TMP, and isopsoralen (angelicin) on hepatic microsomal drug-metabolizing enzymes and cytochrome P-450 were assessed in mice and rats. Administered orally to CD-1 mice daily for 6 days, 8-MOP caused twofold to threefold increases in hepatic aryl hydrocarbon hydroxylase (AHH), ethylmorphine N-demethylase, and cytochrome P-450. The absorbance maximum of the induced cytochrome was at 450 nm. Aniline hydroxylase activity was unchanged. Chronic administration of 8-MOP to Skh:hairless-1 mice caused significant enhancement of hepatic ethylmorphine N-demethylase and cytochrome P-450 but had no effect on AHH, whereas chronically administered TMP had no significant effect on any of these parameters.(ABSTRACT TRUNCATED AT 250 WORDS)