BACKGROUND

Mirodenafil, a phosphodiesterase 5 inhibitor reported to be effective in the treatment of erectile dysfunction, is metabolized by cytochrome P450 (CYP) 3A4 to the active metabolite N-dehydroxyethyl mirodenafil. Mirodenafil may have drug-drug interactions with ketoconazole and/or rifampicin.

OBJECTIVE

The aim of this study was to investigate the effects of a potent inhibitor (ketoconazole) and inducer (rifampicin) of the CYP3A4 isozyme on the pharmacokinetics of mirodenafil to meet the regulatory requirements for the marketing of mirodenafil in Korea.

METHODS

An open-label, 1-sequence, 3-period, 3-treatment crossover study was conducted over 22 days in healthy Korean male volunteers. Each subject received 100 mg of mirodenafil in each of 3 study periods: mirodenafil alone (period 1); mirodenafil after pretreatment with ketoconazole 400 mg once daily for 3 days (period 2); and mirodenafil after pretreatment with rifampicin 600 mg once daily for 10 days (period 3). Serial blood samples were collected for pharmacokinetic analysis after the administration of mirodenafil in each study period. Plasma concentration-time data for mirodenafil and its major metabolite, N-dehydroxyethyl mirodenafil, were determined using LC-MS/MS and analyzed by a noncompartmental method. The results for mirodenafil coadministration with either ketoconazole or rifampicin were compared with those for mirodenafil alone. Adverse events (AEs) were identified by asking general health-related questions of the subjects, by physical examination, and by subject self-report throughout the study period.

RESULTS

Nineteen subjects were enrolled (mean [SD] age, 23.2 [2.76] years [range, 19-29 years]; weight, 69.3 [6.50] kg [range, 61.0-84.0 kg]; body mass index, 22.4 [1.77] kg/m(2) [range, 20.0-26.0 kg/m(2)]) and 18 subjects completed the study. One subject discontinued the study due to protocol violation and was replaced. The AUC(0-infinity) of mirodenafil increased 5.04-fold (90% CI, 3.78-6.72) and the metabolic ratio decreased 0.21-fold after pretreatment with ketoconazole compared with mirodenafil alone. After pretreatment with rifampicin, the AUC(0-infinity) of mirodenafil decreased 0.03-fold (90% CI, 0.02-0.05) and the metabolic ratio increased 2.9-fold. Twelve cases of headache, 6 of nasal congestion, 2 of feeling hot, 2 of epistaxis, and 1 each of dizziness, nausea, and somnolence were considered to be related to administration of mirodenafil. Twenty-eight AEs were reported in period 2 (in 68.4% of subjects), during which systemic exposure to mirodenafil was highest, whereas 7 AEs were reported in period 1 (in 31.6% of subjects) and 5 AEs in period 3 (in 16.7% of subjects).

CONCLUSION

In these healthy Korean male volunteers, the coadministration of ketoconazole and rifampicin resulted in significant changes in systemic exposure to mirodenafil.