Eye doctors want more studies of impotence drug Viagra

May 5, 1998
Web posted at: 11:34 p.m. EDT (0334 GMT)

SAN FRANCISCO (CNN) -- The world's largest organization of eye doctors has called for more study of the popular impotence-treatment drug Viagra, and the physicians warn that patients with some types of eye problems should avoid higher doses.

Some patients taking Viagra have experienced temporary vision problems, including light sensitivity and a bluish tinge in their vision.

The 23,000-member American Academy of Ophthalmology, meeting in San Francisco this week, is urging people to take the problems seriously. The doctors points out that drug's long-term effects are unknown.

"FDA clinical trials show that taking the medication, especially at higher doses, can cause some retinal dysfunction, and affect the way we see for a number of hours," association spokesman Dr. Michael F. Marmor said in a statement.

Pfizer, the pharmaceutical company that developed Viagra, said about 3 percent of the men who tested the drug experienced vision problems, but the trouble went away after a few hours. The company said it plans no further testing.

"Viagra has been extensively tested in 21 clinical trials involving more than 4,000 men. The safety and efficacy results, including effects on vision, were thoroughly reviewed by the U.S. Food and Drug Administration," the company said.

Marmor, a professor of ophthalmology at Stanford University, said a clinical study showed that electrical measures of retinal function dropped by 30 percent to 50 percent and lasted for at least five hours after taking a large dose of Viagra.

He suggested that people with retinal eye conditions such as macular degeneration or retinitis pigmentosa use the drug with caution, staying with the lowest dose possible.

The recommended dose level for most patients is 50 milligrams, according to the FDA.

Dr. Ian Osterloh, a Pfizer researcher, said he suspected a "misunderstanding."

"The drug has been studied extensively," he said. "We have done more studies than have been reported."

The Associated Press contributed to this report.

Related stories:

• Insurers reluctant to pay for new impotency drug - May 1, 1998
• Insurers may limit Viagra coverage - April 29, 1998
• FDA approves pill to treat impotence - March 27, 1998

Related sites:

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• Viagra
• Food and Drug Administration
  • FDA approves impotence pill, Viagra
• Impotence - National Institutes of Health
• Successfully Treating Impotence

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