Viagra

Federal health officials are probing reports of blindness among dozens of men who used Viagra and other impotence drugs -- but at the same time cautioning that the vision loss can be linked to the same illnesses that lead to impotence.

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The Food and Drug Administration disclosed Friday that it was in discussions with the makers of Viagra, Cialis and Levitra about what the labels of those drugs should say about the rare cases of varying degrees of vision loss, including blindness. The maker of Cialis already has voluntarily added a one-line mention to its label.

At issue is sudden vision loss when blood flow to the optic nerve is blocked, a condition called NAION or non-arteritic anterior ischemic optic neuropathy.

The FDA has 43 reports of NAION among the impotence drug users: 38 for Viagra, four for Cialis and one for Levitra, said spokeswoman Susan Cruzan.

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

Also complicating the question: NAION is considered one of the most common causes of sudden vision loss in older Americans, and estimates suggest there are anywhere from 1,000 to 6,000 cases a year. Risk factors include diabetes and heart disease, two of the leading causes of impotence.

Still, "we take this seriously," Cruzan said.

Side effects include vision problems

The questions come at a time when federal regulators and the drug industry are facing criticism about what they do to ensure the safety of drugs already on the market. Pressure on the FDA to investigate reports of side effects has increased since Merck & Co. yanked its pain reliever Vioxx from the market last year because of potentially deadly heart trouble.

Big money is at stake. Pfizer Inc. said in its most recent quarterly filing with the Securities and Exchange Commission that sales of Viagra rose 5 percent -- to $438 million -- in the first quarter of the year.

Pfizer shares declined Friday on the New York Stock Exchange after news of the blindness cases.

Warning labels

-- Viagra: "Less common side effects that may occur are temporary changes in color vision (such as trouble telling the difference between blue and green objects or having a blue color tinge to them), eyes being more sensitive to light or blurred vision."

-- Cialis: "may uncommonly cause ... vision changes, such as seeing a blue tinge to objects or having difficulty telling the difference between the colors blue and green."

-- Levitra: "may uncommonly cause ... vision changes, such as seeing a blue tinge to objects or having difficulty telling the difference between the colors blue and green."

Source: Associated Press

Viagra and its competitors are blockbuster drugs that revolutionized treatment of erectile dysfunction, and they already come with serious warnings: They're not to be used by men who take nitrate-containing drugs, because the interaction could cause deadly drops in blood pressure, or by men with heart conditions