Aim: Vardenafil is a highly selective and potent phosphodiesterase type-5 inhibitor for the treatment of erectile dysfunction (ED). The efficacy of vardenafil has been demonstrated in a broad range of ED populations, but has not yet been assessed in Japanese patients with diabetes mellitus (DM), although DM is frequently associated with difficult-to-treat ED. This is the first study to investigate whether high-dose vardenafil (20 mg) can demonstrate superior efficacy to the usual dose (10 mg) in this subpopulation in Japan.
Methods: The study was a randomized, placebo-controlled, double-blind, multi-centre, parallel group comparison 12-week study. Following 4 weeks observation period, 778 patients aged 26-64 years old with ED and DM (HbA1c >12% at screening was excluded) both of more than 3 years duration were randomly allocated to one of the three groups, vardenafil 10 mg, 20 mg, or placebo (randomization ratio 3:3:1). Erectile function (EF) domain score of the International Index of Erectile Function was estimated as the primary efficacy parameter.
Results: Vardenafil 10 and 20 mg both significantly improved the EF domain score from 13.6 and 13.9 at baseline to 21.8 and 22.9 at last observation carried forward (LOCF), respectively, compared to placebo (13.7 at baseline to 16.3 at LOCF; p<0.0001). In addition, vardenafil 20 mg demonstrated superior efficacy to 10 mg (p<0.05), and the difference was more evident in severe ED patients (baseline EF domain score <11). The safety profile was comparable between these two doses (drug-related adverse events: 6.6, 22.0 and 24.2% in placebo, vardenafil 10 mg, and 20 mg arms, respectively). The most common adverse events were hot flush, headache and nasal congestion, which were mild in intensity and transient, and are known to be common to PDE5 inhibitors.
Conclusion: In Japanese men with DM and ED, vardenafil 10 mg and 20 mg were effective in improving erectile function with comparable safety profiles. Vardenafil 20 mg demonstrated superior efficacy compared with 10 mg, suggesting incremental clinical benefit in using the higher dose in this difficult-to-treat population.