The popular erectile dysfunction drug Viagra® is associated with a number of side effects, but data on long-term harms are still lacking, according to a review of 49 published studies.

In the medical journal Urology, Dr. Alexander Tsertsvadze, from Ottawa Health Research Institute, Ontario, Canada, and colleagues report that men who took Viagra®, also known as sildenafil, were 56 percent more likely than those given a placebo to experience any side effect.

Specific side effects commonly reported by men using Viagra were headache, flushing difficulty breathing, and vision problems.

The results also show that the risk of these side effects increased as the dose of Viagra® rose.

The researchers say more studies are needed with longer follow up, which did not exceed 12 weeks in the studies reviewed.

“More efforts should be directed toward achieving an optimal balance between the degree of effectiveness and safety of sildenafil use in men with erectile dysfunction,” they conclude.

“For example, consideration of flexible dosing regimen of sildenafil to minimize the occurrence of adverse events may be an option,” they wrote.

SOURCE: Urology, October 2009.