NEW YORK (Reuters Health) - Most studies looking at whether erectile dysfunction drugs can help men overcome premature ejaculation problems agree that the pills make a difference, but much of the research is flawed, according to a new review of the evidence.

Of the 14 studies included in the review, 11 found that the medications helped extend the length of time men could have intercourse before orgasm, but Dr. Anastasios Asimakopoulos, lead author of the report, urged caution in interpreting the findings.

"There is still inadequate evidence to propose the use of (these types of drugs) in treating (premature ejaculation)," he wrote in an email to Reuters Health.

The drugs, which go by the brand names Viagra, Levitra and Cialis, are intended to treat men who have problems getting and keeping an erection.

There's been an interest in also using them to address the problem of premature ejaculation, because one of the side effects of the drugs is a delay in ejaculation, the authors write in the Journal of Sexual Medicine.

Asimakopoulos, from the University of Tor Vergata in Rome, Italy, said that anywhere from four to 39 percent of men suffer from premature ejaculation.

His group collected data from 14 studies that measured the effect of medications on extending the time during intercourse before orgasm, technically referred to as the "intravaginal ejaculatory latency time."

Nine of the studies used an erectile dysfunction drug by itself, while four combined the drug with an antidepressant medication, and one combined the drug with behavioral therapy.

Most of the studies asked men to use a stopwatch before and after treatment, to measure if they were able to extend the time having sex.

Some also asked the men to rate changes in their anxiety and sexual satisfaction.

Asimakopoulos and his colleagues ran into problems trying to compare the studies. For one, they didn't always agree on the definition of premature ejaculation.

He said that future studies should use the definition provided by the International Society for Sexual Medicine, which says the disorder involves an inability to last longer than one minute before ejaculating, and includes problems such as frustration or avoiding sexual intimacy.

The other stumbling block to the group's analysis was that fewer than half of the studies compared the drugs to a placebo, a standard for high-quality studies that helps researchers determine whether the drug itself is responsible for any effects seen.

Among four studies, including about 300 men, that did compare an erectile dysfunction medication to a placebo, Asimakopoulos found a positive effect.

After taking a placebo, men had intercourse lasting from about a minute to a little more than a minute and a half.

Among the men who used a medication, intercourse lasted from more than two and a half minutes to about six.

Similarly, the erectile dysfunction drugs, when combined with an antidepressant, worked better than an antidepressant alone.

Asimakopoulos said the results show that these drugs have "a high impact...on prolonging ejaculatory times."

"There seems to be a global positive effect of these drugs in delaying ejaculation; however, the existing evidence is still partial and their role remains controversial," he said.

The drugs are worth further investigation for the treatment of premature ejaculation because antidepressants and topical anesthetics are the only alternatives demonstrated to be effective so far, the team notes in their report.

In future studies, Asimakopoulos said, researchers should not only use a standard definition of premature ejaculation and conduct studies comparing the drug to a placebo, but also shoot for developing a standard and more convenient method of measuring the disorder other than relying on a stopwatch.

SOURCE: The Journal of Sexual Medicine, online January 16, 2012.

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