The U.S. Food and Drug Administration (FDA) knew that Pfizer's Viagra had been linked to blindness at least 13 months before a scientific journal reported the risk, Sen. Charles E. Grassley (R-Iowa) alleges.
Grassley said an FDA safety officer had noted the risk from monitoring adverse event reports and told her supervisors that physicians and the public should be warned. Nothing was done. No public notice was issued and there were no changes to the drug's label.
The series of events is outlined in a letter sent by Grassley to FDA Acting Commission Lester E. Crawford. Grassley said the agency had moved "far too slowly" on identifying and reacting to potential safety issues with the erectile dysfunction drug.
"I am troubled by the FDA's action, or lack thereof, relating to the updating of Viagra's product label," Grassley wrote. He said it was the latest example of inaction involving the FDA's Office of New Drugs (OND).
The FDA has come under fire for failing to alert consumers to potential risks in drugs including Merck's popular painkiller Vioxx, pulled from the market last fire.
The Viagra blindness risk was reported late last month in the Journal of Neuro-Ophthalmology. The journal study examined seven cases where men suffered an unusual form of sudden blindness within 36 hours of taking Viagra.
The rare form of sudden blindness -- non-arteritic anterior ischemic optic neuropathy, or NAION -- is caused by the blockage of blood flow to the optic nerve and is most common in older people, who are the predominant users of Viagra. An estimated 1,000 to 6,000 Americans suffer an optic blockage each year.
Pfizer, meanwhile, denies a connection between Viagra and NAION. In a statement, the company said that problems that can lead to erectile dysfunction tend to be risk factors for NAION as well.
"After more than 10 years of rigorous clinical study and worldwide safety monitoring of a medicine used by more than 27 million men, there is no evidence to suggest a link between Viagra and blindness or other serious ocular events," said Dr. Joseph Feczko, Pfizer's chief medical officer.
The FDA said that 38 Viagra users and five users of other impotence drugs suffered NAION attacks. But in a report Monday, CBS News said the number is much higher, and that more than 800 patients and doctors have reported eye problems to the FDA after using Viagra over the past four years, with more than 140 cases of partial or total blindness.
