The concentration-time profiles of metabolites of moxisylyte, an alpha-adrenergic receptor blocking agent, in the plasma of 12 healthy volunteers were investigated after intravenous (iv) and intracavernous (ic) administrations. The study was conducted in open, randomized, Latin Squares. Plasma levels of moxisylyte and its biotransformation products were assayed by a specific high-performance liquid chromatography method with fluorescence detection. Three metabolites, unconjugated desacetylmoxisylyte (DAM), conjugated DAM, and conjugated monodesmethylated DAM (MDAM), were found in plasma. After iv administration, unconjugated DAM appeared in plasma in < 5 min; the formation of this metabolite is slightly lower after ic administration (half-life, 6.08 +/- 2.33 min). Maximum plasma levels (57.2 +/- 29.4 ng/mL) and area under the curve of concentration versus time (43.3 +/- 11.4 micrograms.h/L) were significantly lower after ic administration than after iv administration (352.8 +/- 287.6 ng/mL and 152.6 +/- 0.247 micrograms.h/L, respectively). For conjugated DAM, the time to reach the maximum concentration is significantly increased after ic administration (0.9 h instead of 0.46 h) and the maximum concentration is significantly decreased (163.5 ng/mL instead of 203.4 ng/mL). The other pharmacokinetic parameters show no change between the two routes of administration. The pharmacokinetic parameters computed for MDAM are in the same range after iv and ic administrations, and there are no significant statistical differences.