Background: Avanafil is a selective phosphodiesterase type 5 inhibitor being developed for the treatment of erectile dysfunction.
Objective: This study was conducted to meet Korean regulatory requirements for the marketing of avanafil. To this end, tolerability and pharmacokinetic properties of single and multiple oral doses of avanafil in healthy Korean male volunteers were assessed.
Methods: A double-blind, randomized, placebo-controlled, parallel-group, dose-escalation study was conducted at the Asan Medical Center (Seoul, Korea). Subjects were randomized to receive either drug or placebo in blocks according to each dose. Subjects were randomly allocated to receive 50-, 100-, or 200-mg tablets of avanafil or placebo once daily for 7 days (avanafil:placebo, 8:2 in each dose group). Tolerability was assessed by monitoring vital signs and results of laboratory tests, 12-lead ECGs, and color discrimination tests. Blood samples of approximately 6 mL were collected in heparinized tubes before and 0.1, 0.33, 0.5, 0.75, 1, 1.5, 2, 3, 4, 6, 8, 12, and 24 hours after drug administration on days 1 and 7. Plasma concentrations of avanafil were measured using LC-MS/MS. Pharmacokinetic parameters of avanafil on days 1 and 7 were determined by noncompartmental analysis and compared among the 3 dose groups.
Results: Of the 32 healthy male subjects initially enrolled, 30 completed the study. The mean (SD) age, height, and weight of the participants were 23.4 (1.7) years, 175.0 (5.4) cm, and 70.3 (8.9) kg, respectively. Adverse events were reported by 20 of 25 subjects (80%) taking avanafil and by 4 of 6 (67%) taking placebo. No serious adverse events were reported, and there were no clinically relevant changes in vital signs, ECG recordings, physical examination findings, or color discrimination test results. All the adverse events resolved spontaneously. Avanafil reached a mean T(max) at 0.33 to 0.52 hour after dosing and then declined, with a mean apparent t1/2 of 5.36 to 10.66 hours. AUC and C(max) were proportional to dose, and the mean accumulation index on day 7 after a single daily dose of avanafil was 0.98.
Conclusion: Avanafil was generally well tolerated and had linear pharmacokinetic properties at daily doses of 50 to 200 mg over 7 days in these healthy Korean male volunteers. Korean National Study Registration Number: 3466.