Dr. Andrew Kramer recently looked over the medical history of one of his patients who had been in the emergency department complaining of chest pains.
Kramer was surprised by what he read: The patient had been taking three to four dietary supplements for erectile dysfunction -- every day.
"I would have never given him Viagra," said Kramer, a urologist at the University of Maryland Medical Center. "He was on the cardiac transplant list."
Heart patients are potentially at risk for a heart attack and an early death when they combine erectile dysfunction drugs, such as Viagra, with heart medications that contain nitrates, like nitroglycerine.
Both drugs lower blood pressure and together can lower it to deadly levels.
Normally doctors won't prescribe Viagra or Levitra to these men, but they can look elsewhere -- specifically, the Internet, where herbal supplements of all sorts are available for sale.
While some of these supplements may contain harmless ingredients, many are indeed as potent as the real thing.
A recent Food and Drug Administration study showed that some of these herbal remedies actually contained the active compound in prescription brands as Viagra, Levitra and Cialis, making them potentially deadly compounds.
The FDA issued a health advisory last week against these supplements.
"These products are promoted and sold on Web sites as 'dietary supplements' for treating erectile dysfunction and enhancing sexual performance, but they are in fact illegal drugs that contain potentially harmful undeclared ingredients."
"These companies are promoting medications that we would never give to men with heart disease," said Dr. Dragan Djordjevic, an internist specializing in male sexual health at Rush University Medical Center in Chicago.
The FDA specifically targeted the herbal supplements Zimaxx, Libidus, Neophase, Nasutra, Vigor -25, Actra-Rx and 4EVERON, all of which do not list the prescription ingredients on their labels.
For this reason, a patient may not realize the risks.
"If they are not eligible for one of the classic drugs, they may go to the supplements, and for this reason, it's more poignant to let the patient know that they can be harmful," said Dr. Yair Lotan, an assistant professor of urology at the University of Texas Southwestern Medical Center in Dallas. "They may buy the supplement and not know they are in danger."
Doctors can't estimate how many men have suffered from this drug interaction because many patients don't reveal that they are on supplements.
In many cases, erectile dysfunction and heart disease are linked. Both are caused by decreased blood flow due to buildup in the arteries.
"A person can come in with severely low blood pressure and die of a heart attack, and not know they should have reported taking supplements," said Dr. Ira Sharlip, a clinical professor of urology at the University of California at San Francisco and spokesman for the American Urological Association.
Given that a large majority of Americans have erectile dysfunction, however, doctors estimate that there are many who have taken or are using these supplements.
It affects about 30 million U.S. men, including more than half of men older than 40, according to Dr. Dominic Carbone, assistant professor of surgery in urology at Wake Forest University Baptist Medical Center in North Carolina.