Table of Contents
It's been known for years that PDE5 inhibitors, Viagra, Cialis, Levitra, improve erectile function in men. However, a surprising number of men in a double-blind, controlled study of sildenafil (Viagra) responded well - better than expected - to placebo as opposed to the active drug. These men reported improved erectile function as measured by International Index of Erectile Function (IIEF)–Erectile Function Domain (EFD) scores.
Methods
Placebo-treated participants in the intent-to-treat population of 42 double-blind, placebo-controlled, flexible-dose, sildenafil studies were included. A participant was classified as a placebo responder if the International Index of Erectile Function-EFD score was ?26 at the last visit.
Outcomes
Variables assessed were:
- age (<45, 45–64, ?65 years),
- race,
- body mass index,
- co-morbidities (cardiovascular disease/hypertension, diabetes mellitus, depression),
- date the last study dose was taken,
- study completion date,
- ED etiology (psychogenic, organic, mixed),
- history of cigarette smoking,
- ED duration, baseline IIEF-EFD score (?10, 11–16, ?17),
- and treatment duration.
Results
- A total of 4,360 men were included; 13.5% were responders.
- Odds estimates indicated the largest likelihood of placebo response occurred in men who were black (odds = 20.2, P < .0001), were younger than 45 years (odds = 7.3, P < .0001), had mild ED (baseline IIEF-EFD ?17; odds >100, P < .0001), and did not have diabetes (odds = 4.5, P < .0001).
- The likelihood of a placebo response decreased as ED duration increased (odds = 0.74, P < .0001).
- The frequency of common adverse events was similar between placebo responders and non-responders.
Conclusions
Certain demographics, co-morbidities, and condition characteristics predicted the odds of a placebo response in sildenafil clinical studies of ED. Underlying reasons behind a placebo response warrant further evaluation. The strong role psychological factors play in ED presentation, even in cases with an underlying organic foundation, can not be overlooked.
"Predictors of Erectile Function Normalization in Men With Erectile Dysfunction Treated With Placebo," Journal of Sexual Medicine,In press, May 2018,
