Placebo Effect in Phosphodiesterase-5 Inhibitor Studies Among Men with Erectile Dysfunction

Many phosphodiesterase-5 inhibitor studies have documented a marked placebo response among patients with erectile dysfunction (ED). This observation led investigators to conduct a meta-analysis of the effect size of this response in 63 placebo-controlled randomized phosphodiesterase-5 inhibitor trials that involved 12,500 patients (mean age, 55). Most studies lasted 8 to 12 weeks. ED changes were assessed in all included studies by validated questionnaires completed before and after treatment.

The effect size of placebo was considered to be small to moderate, compared with the effect size of active phosphodiesterase-5 inhibitors in the pooled analysis. The placebo effect in patients whose ED was caused by post-traumatic stress disorder was c…