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Erectile Dysfunction Drugs Can Lead to Dangerous Interactions

WorstPills.org finds 56 medications that can cause problems

January 5, 2009

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People who take three well-known erectile dysfunction medications should be extremely careful if they take any of 56 other drugs, including many commonly prescribed anti-angina and certain blood pressure medications, grapefruit juice and St. John’s Wort, Public Citizen writes in a new article posted on its WorstPills.org Web site.

The three erectile dysfunction drugs are Viagra (chemical name sildenafil), Cialis (tadalafil) and Levitra (vardenafil).

The 56 drugs fall into three categories:

1) those that can cause a life-threatening drop in blood pressure when taken with erectile dysfunction drugs;

2) those that prevent the body from eliminating erectile dysfunction drugs, thereby leading to an overdose; and

3) those that speed up the metabolism of the erectile dysfunction drugs, thereby reducing their effectiveness.

Grapefruit juice also is listed in the second category because it acts like a drug in this circumstance.

“Those who take erectile dysfunction drugs are generally older men, who are more likely to be taking other medications as well,” said Dr. Sidney Wolfe, director of the Health Research Group at Public Citizen. “It is critical that they be aware of the potential for dangerous interactions.”

Erectile dysfunction drugs cause blood vessels to dilate, an effect that is magnified when taken with blood pressure medications, which also dilate blood vessels. So men who take blood pressure medications such as Flomax and Cardura should avoid erectile dysfunction drugs, Wolfe said.

The combination can cause a dangerous drop in blood pressure that could lead to a heart attack or stroke.

Other drugs, such as erythromycin and nefazodone, inhibit an enzyme that metabolizes erectile dysfunction medications, thereby causing a build-up of the erectile dysfunction drugs to higher levels.

Still other medications, like nafcillin, phenobarbital and 13 other drugs, increase the activity of the enzyme, rendering the erectile dysfunction drugs less effective. St. John’s Wort, an herbal supplement, also falls into this third category because it has a negative, drug-like effect when used with erectile dysfunction drugs.

The complete list of 56 drugs is at Public Citizen’s WorstPills.org, along with an explanatory article from Worst Pills, Best Pills, a monthly newsletter available in print and electronic formats through the subscription site WorstPills.org.

The article about harmful interactions with erectile dysfunction drugs will be available free for the next seven days. The site has other searchable information about the uses, risks and adverse effects associated with prescription medications.

WorstPills.org is an unbiased analysis of information from a variety of sources — including well-regarded medical journals and unpublished data obtained from the Food and Drug Administration — that allows Public Citizen to warn the public about potentially dangerous drugs long before they are banned or adequately regulated by the federal government.

For example, Public Citizen warned consumers about the dangers of Vioxx, ephedra, Baycol and Propulsid years before they were pulled from the market.

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