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Japanese Doctors Figure Out Why Viagra Can Kill

Tuesday, 14 November 2000 12:00 AM

Numerous deaths have been reported among men who used Viagra and then later took nitrates in response to chest pain, or were administered nitroglycerine by others. The use of the combination is warned against by the manufacturer of Viagra, Pfizer Inc. of New York, and medical organizations such as the American Heart Association.

The report, to be published Tuesday in the AHA journal Circulation, "confirms the physiology" of the event that can lead to someone passing out or suffering fatal consequences, said Dr. Nieca Goldberg, chief of cardiac rehabilitation and prevention at Lenox Hill Hospital, New York.

"We have been aware that this combination can be dangerous," said Goldberg, a spokesperson for the AHA at its annual scientific sessions in New Orleans. "We have told our doctors that if you are going to recommend Viagra to a patient with coronary artery disease, the patients should first be taken off nitrates."

"The two drug can be synergistic in their actions, reducing blood flow in compromised coronary arteries and that's what can cause someone to go into cardiac arrest," she said Monday.

In the study, researchers at Osaka University and the Mayo Clinic monitored changes in blood pressure and blood flow through coronary arteries in animals given nitrate along with the doses of Viagra, achieving similar blood levels as prescribed for treatment of erectile dysfunction.

"We found that Viagra, when combined with nitrates, causes a prolonged reduction in blood flow to the heart in critically narrowed coronary arteries," says Bijoy Khandheria, a Mayo Clinic cardiologist and one of the study authors.

"The good news is that Viagra alone did not significantly decrease blood flow through narrowed arteries. In normal vessels, it actually increased blood flow. The negative effect came only when it was combined with nitrates."

"Many heart patients need to take nitrates, and many want to use Viagra. This study shows that they should not be taken together," Khandheria said. "The old adage of taking a nitroglycerine tablet prior to sexual intercourse falls by the wayside if Viagra is prescribed, since the combination can be lethal."

Doctors prescribe nitrates in various forms to relieve or prevent chest pain, known as angina. Common forms include nitroglycerine tablets placed under the tongue, sprays, patches or long-acting tablets.

"Based on our study, we strongly suspect that a death would be induced by a vicious circle," said Khandheria. "The two drugs interact to reduce blood flow in diseased arteries, causing a drop in blood pressure, which deprives the heart of oxygen.

The weakened heart further decreases blood pressure, and the downward spiral continues." Although the studies were performed in dogs, Goldberg said the research would apply to humans. "The dog model is often used to demonstrate coronary blood flow in people. It is an accepted experimental model."

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Numerous deaths have been reported among men who used Viagra and then later took nitrates in response to chest pain, or were administered nitroglycerine by others. The use of the combination is warned against by the manufacturer of Viagra, Pfizer Inc. of New York, and...
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