If you’re a baby boomer who takes erectile dysfunction medications, read this warning

Baby boomers who take three well-known erectile dysfunction medications should be extremely careful if they also take any of 56 other drugs, including many commonly prescribed anti-angina and certain blood pressure medications, grapefruit juice, and St. John’s Wort, warns Public Citizen.

The three erectile dysfunction drugs are Viagra, chemical name sildenafil; Cialis, chemical name tadalafil; and Levitra, chemical name 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 Sidney Wolfe, M.D., director of the Health Research Group at Public Citizen, in a statement about the drugs. "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. 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. Other medications, such as 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 is included in 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.