Current issues of ACP Journal Club are published in Annals of Internal Medicine


Sildenafil improved erections and increased successful sexual intercourse in diabetic men with erectile dysfunction

ACP J Club. 1999 July-Aug;131:3. doi:10.7326/ACPJC-1999-131-1-003

Source Citation

Rendell MS, Rajfer J, Wicker PA, Smith MD, for the Sildenafil Diabetes Study Group. Sildenafil for treatment of erectile dysfunction in men with diabetes: a randomized controlled trial. JAMA. 1999 Feb 3;281:421-6.



Is sildenafil safe and effective for diabetic men with erectile dysfunction (ED)?


Randomized, double-blind, placebo-controlled trial of 12-weeks in duration.


19 U.S. clinical practice centers.


355 men with diabetes mellitus were screened, and 268 (mean age 57 y) were studied. Inclusion criteria were age ≥ 18 years, documented ED for ≥ 6 months, diabetes (type 1 for ≥ 5 y or type 2 for 2 y), stable medical management, hemoglobin A1c level < 0.12, fasting plasma glucose level ≤ 16.6 mmol/L (300 mg/dL), and a stable heterosexual relationship for ≥ 6 months. Exclusion criteria were penile deformities; primary diagnosis of a sexual disorder other than ED; an uncontrolled major psychiatric disorder; spinal cord injury; history of major hematologic, renal, or hepatic abnormalities; recent stroke or myocardial infarction; active peptic ulcer; BP < 90/50 or > 170/100 mm Hg; substantial retinopathy or neuropathy; recent ketoacidosis; or regular use of nitrates or androgens. Follow-up was > 99%, and 96% of men completed the study.


Men were allocated to receive sildenafil (n = 136) or placebo (n = 132) 1 hour before sexual activity not more than once per day. The initial dose of 50 mg could be changed to 25 or 100 mg.

Main outcome measures

Sexual function (International Index of Erectile Function [IIEF]), self-reported global efficacy (improvement of erections), number of attempts and number of successful attempts at intercourse, and adverse effects.

Main results

Men in the sildenafil group had higher mean scores on 13 of 15 questions on the IIEF, a higher rate of improved erections (P < 0.001) (Table), a higher rate of at least 1 episode of successful sexual intercourse (P < 0.001) (Table), and more adverse effects (16% vs 1%, P < 0.001) than did men in the placebo group.


Carefully selected diabetic men with erectile dysfunction who received sildenafil had improved erections and a higher rate of successful attempts at sexual intercourse.

Source of funding: Pfizer, Inc.

For correspondence: Dr. M.S. Rendell, Creighton Diabetes Center, 601 North 30th Street, Suite 6715, Omaha, NE 68131, USA. FAX 402-280-5245.

Table. Sildenafil vs placebo for diabetic men with erectile dysfunction*

Outcomes Sildenafil Placebo RBI (95% CI) NNT (CI)
Improved erections 56.5% 10.2% 451% (229 to 847) 3 (2 to 3)
≥ 1 episode of successful intercourse 60/7% 21.9% 177% (93 to 306) 3 (2 to 4)

*Abbreviations defined in Glossary; RBI, NNT, and CI calculated from data in article.


This study in diabetic men by Rendell and colleagues was modeled on the original clinical trial of sildenafil in a heterogeneous group of men with ED (1). The 2 trials show similar improvement in self-assessed erectile function and the ability to have intercourse in a 12-week treatment period. The response rate was less favorable in this study than that in the previous study, underscoring the more complex and severe causes of ED in diabetic men than in the larger group that contained some men with pure psychogenic causes of ED. For this study, patients were carefully screened to exclude those with additional complicating causes, such as severe neuropathy, and to include those who had good diabetic control and no risk factors for sildenafil toxicity. Many patients in standard clinical practice, however, may not fit this study's inclusion criteria, and the treatment may be less successful in clinical practice than in this trial. Although side effects were common in the treatment group, the rate of discontinuation of therapy was actually lower in the treatment group (4%) than in the control group (8%). This was also seen in the previous study (1).

These data provide compelling evidence for the safety and efficacy of sildenafil, and they support the widespread use of this agent for many men with ED. However, it is important to remember that ED is most often a medical problem that demands an adequate work-up with a history, a physical examination, and appropriate laboratory tests to rule out reversible causes (2). Although sildenafil may be effective, it is contraindicated in patients receiving nitrates and must be used with caution (3). Further, both the patient and the partner should be informed about other therapies for ED so that they can make a rational treatment decision.

Sender Herschorn, MD
University of TorontoSunnybrook and Women's Health Sciences CentreToronto, Ontario, Canada


1. Goldstein I, Lue TF, Padma-Nathan H, et al. Oral sildenafil in the treatment of erectile dysfunction. Sildenafil Study Group. N Engl J Med. 1998;338:1397-404. Erratum. 1998;339:59.

2. NIH Consensus Conference. Impotence. NIH Consensus Development Panel on Impotence. JAMA. 1993;270:83-90.

3. Cheitlin MD, Huter AM Jr, Brindis RG, et al. ACC/AHA expert consensus document. Use of sildenafil (Viagra) in patients with cardiovascular disease. American College of Cardiology/American Heart Association. J Am Coll Cardiol. 1999;33:273-82.