Concerns about the interaction between erectile dysfunction (ED) drugs and nitrates were first aired a decade ago, says Randall Zusman, M.D., a cardiologist at the Massachusetts General Hospital Heart Center who conducted some of the early research. All three ED drugs now carry warnings about the risk.

Men with ED typically have some artery blockage, Zusman says, and these drugs work by dilating the blood vessels to improve blood flow. Patients whose artery blockage is severe enough to cause chest pain may be prescribed nitrates — whether in a patch, a long-lasting oral form or a fast-acting nitroglycerin pill placed under the tongue — to alleviate their symptoms.

When the drugs are combined, there may be a powerful reaction, with blood pressure dropping 50, 60 or 80 points in 30 minutes, Zusman said. The mildest side effect might be a feeling of light-headedness, or a patient may faint. A more severe blood pressure drop could trigger kidney failure or a stroke. A patient who visits an emergency department complaining of chest pains should volunteer whether he has taken an ED drug.

Although sexual activity slightly raises the risk of triggering a heart attack, the good news is that for most patients with cardiovascular disease the risk is minuscule, according to Levine. “In the hour around and immediately after sexual activity, the risk of heart attack does go up by two to three times,” he says, “but when you look at a patient’s total overall risk of having a heart attack, this really represents a very small contribution.”

It’s vital for both patient and physician to discuss these issues forthrightly, Zusman said. “If the physician doesn’t inquire whether the patient is sexually active and has ED and the patient doesn't offer, then you never get to the discussion of whether you can [take ED drugs] safely.”

Also of interest: How to talk to — and understand — your doctor.

Michael Haederle is a freelance writer whose work has appeared in People, the New York Times and the Los Angeles Times.