Fluconazole and testosterone: in vivo and in vitro studies.

Fluconazole (UK-49,858), a novel bis-triazole antifungal agent, was given orally to groups of 10 male volunteers at doses of 25 and 50 mg/day for 28 days. Blood samples for testosterone estimation were taken from these and from a placebo group at several time points on days 1, 14, and 28 of the study, and the assay results demonstrated that the compound had no significant effect on circulating testosterone levels. Similarly, in studies with rat Leydig cells in vitro, fluconazole at concentrations up to 10 micrograms/ml was found to be only a weak inhibitor of testosterone production, whereas ketoconazole caused more than 50% inhibition at 0.1 microgram/ml. It is concluded that fluconazole, in contrast to ketoconazole, has little effect on the biosynthesis of testosterone by mammalian cells.