Viagra blindness risk claims

‘s Viagra, but have not determined if the medicines were responsible.

The Food and Drug Administration said it has about 38 reports of the rare condition among Viagra users, four reports among users of Eli Lilly and Co.’s Cialis and one report in a man who took GlaxoSmithKline Plc’s Levitra.

More than 23 million men worldwide have taken Viagra over the past seven years, Pfizer said. Reports are extremely rare of the condition known as non-arteritic anterior ischemic optic neuropathy (NAION), the company said.

NAION can cause permanent vision loss in one or both eyes.

“FDA is aware of these reports but has not determined there is a cause and effect due to use of Viagra … We’re working with the company to make sure this information is available to doctors and patients,” said FDA spokeswoman Susan Cruzan.

New York-based Pfizer said it is weighing a change to the Viagra label.

However, it emphasized no proof exists that links the blindness to the drug, which was introduced in 1998 and had $1.68 billion in sales in 2004.

“While we expect the FDA to take these cases seriously, we do not believe they warrant concern with the product at this time,” AG Edwards & Sons analyst Al Rauch said in a research note.

The news pushed shares of Pfizer, a component of the Dow Jones industrial average, down more than 2 per cent, weighing on the broader market.

Viagra’s label currently lists the most common side-effects as headache, facial flushing and upset stomach, and says less common events are bluish or blurred visions and sensitivity to light that may occur for a short time.

“There is no evidence showing that NAION occurred more frequently in men taking Viagra than men of similar age and health who did not take Viagra,” Pfizer said in a statement.

Dr Michael Berelowitz, Pfizer’s vice-president for worldwide medical, said in an interview he did not think the FDA would require a “black box” warning — the strongest for prescription drugs — about the NAION reports.

Pfizer contacted the FDA about the blindness cases in March, after a study in the Journal of Neuro-Ophthalmology reported seven NAION cases in Viagra users, Berelowitz said. The study said the cases occurred within 36 hours after the men took Viagra.

All of the patients had high blood pressure, diabetes or elevated cholesterol — conditions that raise the risk of NAION, the study said. All developed some degree of blurred vision or vision loss in one eye, while one patient had the problem in both eyes.

“It’s quite hard to see causality” between the vision loss and Viagra use, Pfizer’s Berelowitz said.

The FDA said patients should contact a doctor if they have questions about the drugs or the condition.

Eli Lilly changed the Cialis label earlier this week to note the reports of NAION, company spokeswoman Kindra Strupp said. Five million men have taken the drug, she said.

GlaxoSmithKline officials could not immediately be reached for comment. The FDA will talk with GlaxoSmithKline about the Levitra label, Cruzan said.

FDA critic Sidney Wolfe said the agency should mandate a black-box warning for all three impotence pills, even though the blindness problem appears rare.

“The trade-off between blindness and something that could be remedied by some psychological counseling is a really bad trade-off,” said Mr Wolfe, director of Public Citizen’s Health Research Group.