Popular drugs used to treat erectile dysfunction - Viagra, Levitra and Cialis - are safe and effective for men with diabetes, a new review has found.

The introduction of the medications known as phosphodiesterase type 5 (PDE-5) inhibitors to the market has changed the way physicians manage their patients with erectile dysfunction. The drugs have been shown to be quite effective in treating the condition in the general population and the number of men requesting them has soared in recent years.

The aim of the systematic review, however, was to determine whether PDE-5 inhibitors such as sildenafil (Viagra), vardenafil (Levitra) and tadalafil (Cialis) are also a safe and effective option for men with diabetes. Although diabetes can causes a variety of other chronic complications, such as heart disease and high blood pressure, PDE-5 inhibitors were shown not to cause many adverse reactions in this group.

At the end of the studies, men who took PDE-5 inhibitors showed improvements on all measures of erectile function, with an average difference of 26.7 percent more “successful intercourse attempts” compared to placebo groups.

The review appears in the current issue of The Cochrane Library, a publication of The Cochrane Collaboration, an international organization that evaluates research in all aspects of health care. Systematic reviews draw evidence-based conclusions about medical practice after considering both the content and quality of existing trials on a topic.

“The results of our meta-analysis are not surprising, but give strength to the general notion that this class of drugs is efficient and safe for this specific wide population,” said lead author Moshe Vardi, M.D., with the internal medicine division at Lady Davis Carmel Medical Center in Israel.

The Cochrane reviewers analyzed eight studies that compared the effectiveness of the three PDE-5 medications to placebo. A total of 1,759 men were recruited - with roughly half randomized to receive PDE-5 inhibitor therapy and the rest to the placebo group. Overall, 80 percent of the participants had type 2 diabetes and the others had type 1 diabetes.

Most of the studies lasted for 12 weeks, with no significant differences among treatment groups with regard to age, medical history, other prescribed medications or severity or duration of diabetes or erectile dysfunction.

Erectile dysfunction is defined as the repeated inability to get or maintain an erection firm enough for sexual intercourse. According to the National Institute of Diabetes and Digestive and Kidney Diseases, men who have diabetes are three times more likely to have erectile dysfunction than men who do not have diabetes.

Taken an hour before sexual activity, PDE-5 inhibitors work by enhancing the effects of nitric oxide, a chemical that relaxes smooth muscles in the penis during sexual stimulation and allows increased blood flow.

“PDE-5 inhibitors have been considered the mainstay of treatment for erectile dysfunction in the general population for many years,” said Vardi. “Diabetics are prone to this complication, and the etiology of their erectile dysfunction is multifactorial, thus making their treatment a special challenge for physicians and other health care professionals.”

No deaths were reported in any of the included trials; the most common side effects for men in the treatment groups were headache, flushing and upper respiratory tract complaints and flu-like symptoms. The overall risk for developing any adverse reaction was 4.8 times higher in the PDE-5 group than in the control group.

As with any drug therapy, the Cochrane reviewers caution that men should use PDE-5 inhibitors only as directed by their physicians.

“These drugs can be taken on an ‘as needed’ basis, as their half-life spans from several hours to 48 hours at most,” said Vardi. “Patients should also consult their physicians for drug-drug interactions and specific contraindications.”

While this review supports the short-term safety of these medications for men with diabetes, experts say as yet there is no concrete evidence whether these medications are safe for the long term.

“I prescribe PDE-5 inhibitors every day to people with diabetes,” said John Buse, M.D., director of the Diabetes Care Center at the University of North Carolina School of Medicine. “But whether they are safe [in the long term] is the essential quandary of all medical care. We make our best guesses based on imperfect information, hopes and fears. And then we monitor progress. I am impressed that patients with diabetes in my practice in 2006 are living much better lives and perhaps longer lives than they did 10 years ago.”

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