Viagra May Cause Blindness
Pfizer, the world’s largest pharmaceutical company, may have to place warnings on boxes of Viagra to say that its best-selling impotence drug causes blindness in some people.

America’s drug regulator, the Food and Drug Administration, said yesterday it had received reports of 38 cases of blindness which appeared to have been caused by Viagra, and a further four cases among patients taking Cialis, the number two drug in the erectile dysfunction market, made by Eli Lilly.

The FDA said it was investigating the link between the sight problems and the drugs, but has not discovered whether there is a direct connection.

"We take this seriously," a FDA spokeswoman said.

Pfizer and other manufacturers already warn patients on their websites that sight problems such as blurring can be a rare side effect of taking impotence drugs. The FDA may force them to add the specific disclosure about the risk of blindness to labels on bottles.

Pfizer said it was talking to the FDA about adding a disclosure to Viagra’s label to say that in rare cases men taking Viagra had developed blindness.

The company said reports of blindness had surfaced before, but added that no proof had been found of a direct link with Viagra. It said men who take Viagra often have high blood pressure and high cholesterol, which are also associated with the conditions that can cause blindness.

Pfizer’s shares fell 3 per cent in New York, as the problem appeared to be just the latest in a series of safety concerns to hit the drug industry. Viagra, introduced in 1998, had sales of US$1.68bn in 2004. Levitra, made by GlaxoSmithKline and Germany’s Bayer, was approved in August 2003, and Cialis in November of that year. Shares of GSK rose.

GSK said it has not found any evidence that Levitra, the third largest erectile dysfunction drug which it manufactures in the US, has caused sight problems.