Viagra and similar drugs seem safe for the short term, but their long-term health effects haven't been studied.

RODALE NEWS, EMMAUS, PA—When a guy wants his equipment to work, he wants it ASAP, not next year or even the next day. Which is one reason Viagra and other brands of erectile dysfunction medication are so popular. Yet two studies, published this month in the medical journals Urology and Annals of Internal Medicine, illustrate the need for a more future-oriented focus when it comes to these medications—and, specifically, their long-term side effects. Which, at this point, are a big, fat question mark.

THE DETAILS: Two teams of researchers, both headed by Alexander Tsertsvadze, MD, an epidemiologist with the Ottawa Health Research Institute in Canada, reviewed a total of 240 studies of drug and hormonal treatments of erectile dysfunction, defined as the “persistent inability to achieve or maintain an erection sufficient enough for satisfactory sexual performance.” In both instances, the teams found few studies of more than 12 weeks’ duration—meaning that no one knows much about the effects of Viagra and similar kinds of erectile dysfunction medication over the long term.

In the short term, however, the studies found that the family of medicines that include Viagra and other oral phosphor-diesterase-5 (PDE-5) inhibitors improved erectile functioning better than a placebo. They also had more adverse side effects than a placebo, although most of those side effects were mild to moderate, such as headache, flushing, upset stomach, and runny nose.

WHAT IT MEANS: Viagra works, and it is safe for most people—at least as a short-term solution to erectile dysfunction. In fact, based on the results of Dr. Tsertsvadze’s work, the American College of Physicians issued new clinical guidelines for the pharmacologic treatment of erectile dysfunction this week. Recommendation #1: “Clinicians initiate therapy with a PDE-5 inhibitor in men who seek treatment for erectile dysfunction and who do not have a contraindication to PDE-5 use.” The only contraindication to PDE-5 use found in the studies is the concurrent use of nitrate drugs: Any man taking nitrates for chest pain should never take Viagra as well.

But data on long-term use of these drugs just isn't there. “The rates of serious adverse events in these trials were very low (less than 2 percent) and similar in men who received oral PDE-5 inhibitors and those on placebos,” says Dr. Tsertsvadze. “But we don’t have any long-term follow-up data that’s reliable, so we can’t arrive at definitive conclusions about long-term harms.” If you’ve taken Viagra for six months or more, asserts Dr. Tsertsvadze, you’re in “data-unknown” territory.

Here’s how to make the most of what’s known about erectile dysfunction: