Viagra, Nitrates Do Not Mix

Since it was approved in April, 39 patients who used Viagra have died, reports CBS News Correspondent John Roberts.

Six of the men died after taking the drug in conjunction with nitroglycerin or nitrates - common drugs for treating chest pains and heart attacks.

"The risk of the combination of Viagra and nitrates is very, very high." said Dr. Adolph Hutter of Massachusetts General Hospital. "It can cause a profound drop in blood pressure and lead to disastrous situations."

In their recommendations Monday, the American College of Cardiology and the American Heart Association warned emergency physicians not to give nitrates to patients within 24 hours of taking Viagra.

Cardiologist Ezra Deutsch says the Viagra phenomenon adds another unknown into life and death decision making.

"It means we have to ask yet another question in terms of medical history to determine whether these patients have taken a medication like Viagra in the last 24 hours," he said.

The recommendations also caution against using Viagra in other patients, such as those with poor blood flow to the heart, congestive heart failure, and patients taking multiple drugs to control high blood pressure.

Currently, the only U.S. warnings against using viagra are for patients taking nitrate medication. However, when it is approved for use in Europe, Viagra is expected to carry far more comprehensive warnings, including those for patients with certain types of cardiovascular disease.

"They are being more circumspect and a little more cautious based on the rash of events that happened once the drug was approved in the U.S.," said Dr. Deutsch

Pfizer, the company that makes Viagra, said it welcomes the warnings to doctors about nitrates. However, the company says it has no plans to strengthen U.S. labels to reflect any other concerns.

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