Dear DOCTOR Owen:

I took the diet medication Phentermine and fenfluramine (Phen-fen) for three months. I worry that I have heart valve damage that may show up later in life. I took one Redux (fenfluramine) tablet/day (20 milligrams). I understand that this drug has been implicated in causing valve problems. What is the latest in this investigation?

Fat Without Fen

Dear “Fen”:

There has been intense investigation of this subject since Mayo Clinic doctors discovered the heart valve leak associated with use of these drugs. It was found that a small, but significant, percentage of patients were developing leaking aortic and mitral heart valves. A material was found on several of the valves—caused by large amounts of serotonin in the bloodstream. A tumor, known as carcinoid, has been known to cause this same phenomenon for almost a century. Carcinoid produces large amounts of serotonin. Therefore, the doctors believed that the serotonin levels increased by fenfluramine may have caused the valve problem, similar to carcinoid tumors. (Elevated serotonin levels also improve satiety.)

Subsequent studies have shown an association, albeit small, between heart valve leaks and Phen-fen. Two articles published in 1999 should help with your anxiety:

• Researchers at the Centers for Disease Control, in cooperation with the Food and Drug Administration (FDA), reported on their findings in the International Journal of Obesity, Vol. 23, 926–928. They found very significant heart valve leaks in patients who took more than 60 milligrams of fenfluramine/day. They also noted a tendency for increased risk in people who took the drug for more than six months. These findings have been seen in other smaller studies around the country. The incidence reported so far is in the range of 3%–15%, with higher risk in larger and longer dosing.
• In another study reported by Pennington Biomedical Research Lab in Baton Rouge, Louisiana, patients with heart valve leaks who took Phen-fen were followed for more than a year. Most of the cases showed resolution of the leaks without any treatment. The researchers also found an increased risk with higher and longer used doses of Phen-fen. Those with the shortest duration of use resolved the fastest.

I recommend that you see a cardiologist who uses echocardiography (ECHO), even if your physician does not hear a leak. Only an ECHO of the heart will show leaks, which cannot be heard with a stethoscope. These leaks rarely cause symptoms. Many of the patients in both studies had no sounds of leaks on examination, and a small percentage of the population who never took medication had leaks in their heart valves.

The medication comprising the first component of “Phen”-fen is Phenteramine. There are no indications that the Phentermine caused or contributed to the valve problem. Phentermine does not affect serotonin, and is the ingredient in Ionamin, Adipex, and similar “diet” pills.

I ask every patient who expresses an interest in taking a diet pill: “Are you ready to take it forever?” The same applies to the popular over-the-counter diet pills. Unless changes in diet and exercise are made, weight and appetite will return as soon as the pill is discontinued. Originally, it was thought that diet pills would “jump start” patients, who would miraculously acquire motivation on seeing success. The data, however, do not support this assumption.

Diet pills do work, and may be safe when taken over the long term. However, the risk and the benefit should continuously—and always—be weighed.