WASHINGTON — An investigation into whether Viagra and other popular impotence drugs may cause permanent eye damage is unlikely to lead to a recall, federal officials and medical experts said Friday, but could prompt new warnings.
The Food and Drug Administration is looking into 38 reports of eye damage in men who took Viagra, four reports involving Cialis, and one linked to Levitra. About 30 million men worldwide have taken the drugs.
"We haven't been able to determine that there is a cause and effect due to the medication," FDA spokeswoman Suzanne Trevino said. "But we are taking it seriously."
Most of the men who suffered eye damage did not go completely blind, but lost partial vision in one eye. Complicating the FDA's investigation, many of the patients had other risk factors, such as high blood pressure, that would make them vulnerable to that kind of eye problem.
The condition -- nonarteritic anterior ischemic optic neuropathy, or NAION -- involves damage to the optic nerve caused by an interruption of blood supply.
Trevino said the FDA was talking with Pfizer Inc., Viagra's manufacturer, about formally disclosing the risk in prescribing literature for doctors.
Eli Lilly & Co., which makes Cialis, recently changed its information to acknowledge reports of eye damage.
Dr. Howard Pomeranz, a professor of ophthalmology at the University of Minnesota, reported a suspected link between Viagra and eye damage in a medical journal article published in March.
"This particular eye problem should be added to the list of side effects that patients have access to," Pomeranz said Friday. But, he added, the medical evidence at this point would not warrant withdrawing the drug.
"I'm not recommending that men stop taking this drug," he said. "It's very good for what it's prescribed for."
However, Pomeranz said, patients who already have NAION in one eye should be strongly cautioned about the risk of using Viagra. And any patient who experiences blurriness or a loss of peripheral vision should stop taking such medications and consult a doctor immediately, he said.
For patients who want to know whether they are at risk, an eye exam may help answer the question. Doctors say one risk factor for NAION is tightly bundled nerves and blood vessels in the back of the eye. An eye doctor can identify that condition.
Factors that increase the risk of NAION include high blood pressure, high cholesterol and diabetes. Older people also are more likely to have the problem.
