Safety, tolerability and pharmacokinetics of udenafil, a novel PDE-5 inhibitor, in healthy young Korean subjects

AIM To evaluate the safety, tolerability and pharmacokinetics (PK) of udenafil, a novel phosphodiesterase type 5 inhibitor. METHODS A double-blind, randomized, placebo-controlled, dose-rising, parallel-group, single- and multiple-dose study was conducted in healthy Korean subjects. The subjects were allocated to single-dose groups of 25, 50, 100, 200 or 300 mg (eight subjects in each dose group, including two placebos), or to multiple-dose groups of 100 or 200 mg (once-daily dosing for 7 days; nine subjects in each dose group, including three placebos). Serial samples of blood and urine were collected after oral administration and the drug concentrations in plasma and urine were determined by high-performance liquid chromatography. Safety and tolerability were evaluated by monitoring clinical laboratory parameters and adverse events. RESULTS Udenafil reached peak plasma concentrations at 0.8-1.3 h, and then declined mono-exponentially with a terminal half-life of 7.3-12.1 h in the single- dose study. The area under the time-concentration curves (AUC) and maximum plasma concentrations (C-max) increased supraproportionally with increasing dose in the single- dose study. During multiple dosing, a steady state was reached at 5 days and little accumulation occurred after repeated dosing for 7 days. Udenafil was generally well tolerated in these healthy subjects, and no serious adverse events occurred. CONCLUSIONS Udenafil was safe and well tolerated in healthy volunteers. The AUC and Cmax of udenafil increased supraproportionally with increasing dose upon single administration, but there was no significant drug accumulation upon multiple administrations.