Differences in side-effect duration and related bother levels between phosphodiesterase type 5 inhibitors

To assess whether the longer half-life of tadalafil is associated with longer lasting or more severe side-effects than the other phosphodiesterase type 5 inhibitors (PDE-5Is), as clinical trials have shown that the efficacy and safety of the three available are similar, but tadalafil has a half-life four times longer than the other two drugs.

Treatment-naive men beginning PDE5-I therapy were recruited from a specialist clinic. Data on the type and duration of drug-associated side-effects were collected prospectively. Levels of bother were assessed with a visual analogue scale (VAS). Differences in type, duration and bother of side-effect were compared between drugs.

In all, 409 men provided data; there were no differences between drugs in the proportion of men responding, or the overall prevalence of side-effects. The mean duration of side-effects with tadalafil was 14.9 h, compared to 3.9 and 7.7 h for sildenafil and vardenafil. Of men taking tadalafil, 30% had side-effects lasting >12 h. There were no differences in mean VAS scores between the drugs. Individual side-effects caused similar levels of bother, except for facial flushing, which was less bothersome.

Men taking tadalafil are at risk of prolonged side-effects, although levels of bother associated with these side-effects are not significantly greater than those seen with short-acting PDE5-Is.