I Goldstein, for the Sildenafil Study Group [Broston Univ; et al]
Oral Sildenafil in the Treatment of Erectile Dysfunction
N Engl J Med 338: 1397-1404, 1998
Introduction – Sildenafil [Vaigra],a selective and potent inhibitor of cyclic guanosine monophosphate in the corpus cavernosum, restores the natural erectile response to sexual stimulation in men with erectile dysfunction. The oral therapy offers advantages over previously available treatments that required injections, prostheses, or surgery. Two sequential studies evaluated the efficacy and safety of sidenafil in men with erectile dysfunction of organic, psychogenic, or mixed causes.
Methods – 2 studies were conducted, a study of dose response and a dose escalation study. In a study of dose response, efficacy, and safety ,532 men were randomly assigned to receive 25, 50 or 100 mg of sildenafil or placebo for 24 weeks. Tablets were to be taken approximately 1 hour before sexual activity. The 12 week dose -escalation study included 329 different men, randomly assigned to receive placebo or 50 mg of sildenafil 1 hour before activity. Participants were able to double or reduce the dose by 50% according to therapeutic response and adverse effects. The men were questioned about their frequency of penetration and maintenance of erections after penetration.
Results – The dose response study showed an association between improved erectile function and increasing doses of oral sildenafil. Regarding achievement of erections, men who received 100 mg of the drug increased their mean score by 100% [to 4.0 after treatment vs. 2.0 at baseline, from a possible score of 5.0].
In the dose-escalation study, 69% of attempts at sexual intercourse during the last 4 weeks of the study were successful in the sildenafil group. The success rate in the placebo group at this time was only 22%.
The mean number of successful attempts at sexual intercourse was 5.9 per month in the sildenafil group vs. 1.5 per month in the placebo group.
10% of men in the sildenafil group and 17% in the placebo group stopped treatment because of adverse effects; corresponding figures for the dose-escalation study were 6% and 8%.
The most common adverse effects, reported by 6% to 18% of men, were headache, flushing and dyspepsia.
Discussion – Sildenafil improved sexual function in men with erectile dysfunction, causing erection in response to sexual stimulation. The therapeutic response to the drug was similar in men with various causes of erectile dysfunction. Increasing doses, from 25 to 100 mg, improved the frequency of penetration. Sildenafil is simple to use and is generally well tolerated.