RESUMO
INTRODUCTION: Randomized clinical trials (RCT) remain the gold standard in providing scientific evidence in medical practice in spite of the significant placebo effect in the treatment of several disorders. Although the first-line therapy for erectile dysfunction (ED) is oral phosphodiesterase type-5 inhibitor (iPDE5), the placebo effect in RCT of iPDE5 for ED occurs at a rate as high as 50%. AIMS: To evaluate the role of therapeutic illusion in the oral treatment for ED. METHODS: A prospective, controlled, single-blind, parallel-group study was performed at single-center. One hundred and twenty-three patients with ED were randomly assigned into three groups and received different letters: Group 1 (G1) was informed to be receiving a substance for ED treatment; Group 2 (G2) was informed that they could be receiving an active drug or placebo; Group 3 (G3) was conscious to be using placebo. Starch capsules were dispensed to all patients. Median follow up was 12 weeks. MAIN OUTCOME MEASURES: ED improvement was assessed after 8 weeks of the intervention by the erectile function domain of the International Index of Erectile Function (IIEF) and the Quality of Erection Questionnaire. ED severity was classified by the IIEF erectile function (IIEF-EF) domain score into five categories: no ED (score of 26-30), mild (22-25), mild to moderate (17-21), moderate (11-16), and severe (6-10). Improvement in IIEF-EF domain was considered as a change in category of severity. RESULTS: ED severity improved in all three groups (G1 = 31.7%, P = 0.039; G2 = 36.8%, P = 0.028; G3 = 36.8%, P = 0.002) and no difference was found among groups (P = 0.857). Improvement of quality of erection score was only significant in G2 (P = 0.005) and G3 (P < 0.001). CONCLUSIONS: Written-suggested therapeutic illusion for patients with ED has no major influence in the outcomes. However, treatment of ED with oral placebo capsules demonstrates clinical effects, improving erectile function and quality of erection.