Diabetes mellitus not infrequently causes erectile dysfunction. Rendell and colleagues conducted a randomized placebo-controlled 12-week trial to determine if sildenafil is efficacious in the treatment of erectile dysfunction in patients with diabetes.

The multicenter double-blind flexible-dose study enrolled 268 men with at least a five-year history of type 1 diabetes or a two-year history of type 2 diabetes. They ranged in age from 27 to 79 years, and erectile dysfunction had been present for at least six months. Excluded from the study were patients with penile deformity, major psychiatric disorders, spinal cord injuries, recent myocardial infarction, recent stroke, peptic ulcer disease, hypotension or hypertension. All patients had a history and physical examination as well as blood tests.

After a four-week period in which no treatment was given, patients were randomly assigned to receive placebo or sildenafil in an initial dosage of 50 mg, taken once daily as needed. The 50-mg dosage was increased to 100 mg or decreased to 25 mg at the discretion of the investigator after the efficacy and tolerability of the 50-mg dosage was assessed. The International Index of Erectile Function, a 15-question validated measure of erectile dysfunction, was used to determine whether the treatment had improved penile erections. Patients also kept a log of the number of successful and unsuccessful attempts at sexual intercourse.

The sildenafil group comprised 136 patients, and the placebo group comprised 132 patients. By the end of the study, 126 patients (93 percent) in the sildenafil group were taking 100 mg of the drug, and 10 patients (7 percent) were receiving 50 mg.

Patients who received sildenafil were significantly more likely than patients taking placebo to report improved erectile function. Erections were improved in 74 (56 percent) of 131 men in the sildenafil group versus 13 (10 percent) of 127 men in the placebo group. Specific improvements were noted in orgasmic function, sexual satisfaction and overall satisfaction. Sexual intercourse was successful at least once during the study period in 61 percent (71 of 117) of the treatment group, compared with 22 percent (25 of 114) of the placebo group. The sildenafil group overall had almost four times more successful intercourse attempts than the placebo group.

Adverse events in the sildenafil group included headache, dyspepsia and sinus congestion. Adverse events in both groups were transient and mild to moderate.

The authors conclude that sildenafil, known to be effective in men in the general population with erectile dysfunction, is also effective and safe in men who have erectile dysfunction associated with diabetes.