FDA issues
warnings on impotence drugs

The government on Friday ordered warnings onto the labels of Viagra and two other impotence drugs that some users have developed a form of blindness--while cautioning that it's impossible to know if the pills are to blame. At issue is sudden vision loss when blood flow to the optic nerve is blocked, a condition called NAION, or nonarteritic anterior ischemic optic neuropathy. NAION is considered one of the most common causes of sudden vision loss in older people, with anywhere from 1,000 to 6,000 cases a year. Moreover, risk factors include diabetes and heart disease, two of the leading causes of impotence.

The Food and Drug Administration has 43 reports of NAION among the impotence drug users: 38 for Viagra, four for Cialis, and one for Levitra. They include varying degrees of vision loss, including blindness.

Those are rare numbers, given that Viagra alone has been used by 23 million men worldwide since its approval in 1998, according to its maker, Pfizer.

"It is not possible to determine whether these oral medicines for erectile dysfunction were the cause" or whether other health conditions triggered NAION in the men, the FDA said in a statement Friday. In addition to heart disease and diabetes, NAION risk factors include being over age 50, high blood pressure, high cholesterol, and smoking.

But the FDA advised patients to stop taking the pills and call a doctor if they experience sudden or decreased vision loss in one or both eyes--and to tell their doctor if they have ever suffered an episode of sudden vision loss, because such patients are at increased risk of a second episode.

Studies have shown that gay men are more likely than their heterosexual peers to have tried or to regularly use erectile dysfunction drugs like Viagra, Cialis, and Levitra. The drugs are also commonly taken by users of such illegal party drugs as crystal methamphetamine and ecstasy to help counter erection-inhibiting effects of the drugs or to prolong erections to allow sexual encounters with multiple partners. (AP, with additional reporting by Advocate.com)