Preference for and adherence to oral phosphodiesterase-5 inhibitors in the treatment of erectile dysfunction.

Sildenafil was the first orally administered phosphodiesterase-5 inhibitor approved for the treatment of erectile dysfunction. Its successful introduction into clinical practice was soon followed by the launch of two other phosphodiesterase-5 inhibitors: vardenafil and tadalafil. The plethora of choices made the question "which PDE-5 inhibitor?" relevant for patients and clinicians. Despite the lack of head-to-head comparative trials it is widely accepted that there are no significant differences in their safety and efficacy. Therefore a number of studies set out to determine which of the inhibitors patients would prefer and reasons for that preference. The majority of published trials show a preference for tadalafil. Others have argued that preference trials have several methodological flaws and data favoring tadalafil with its long duration of action do not reflect real-life prescription filling and sales figures. But even if one of the available PDE-5 inhibitors is chosen to treat erectile dysfunction what is the long-term compliance? A significant percentage of men initiating treatment switch between inhibitors or discontinue therapy. Reasons for that seem to often be unrelated to efficacy or tolerability and include emotional and social factors determining couples' and individuals' sexual and treatment seeking behavior.