Dexfenfluramine and fenfluramine withdrawn from market
On September 15, 1997, the U.S. Food and Drug Administration (FDA) announced the withdrawal of dexfenfluramine (brand name REDUX) and fenfluramine (brand name Pondimin) from the market. The section on "what will happen in the future" was updated in 2001.
What was found?
It has been reported in March, 1997 ( U.S. data) and a few years back (European literature) that unusual heart valve abnormalities which resulted in "leaky" heart valves were being detected in individuals on fenfluramine and/or dexfenfluramine used in association with phentermine ("phen/fen"). In July 1997, the Mayo Clinic released the results of a study which was subsequently published in the New England Journal of Medicine (August 28, 1997). Since then, many more cases have been reported to the FDA's MedWatch Program. Most of the reported cases involve the aortic and/or mitral valve. Several studies were then undertaken in an attempt to determine the incidence of these abnormalities. The studies appear to indicate that up to 32% of individuals who were on dexfenfluramine or fenfluramine with or without phentermine may be afflicted with these leaky heart valves. For comparison, the incidence of these abnormalities in the general and obese population is just over 1%. These finding prompted the FDA to ask American Home Products/Wyeth-Ayerst and Interneuron Pharmaceuticals to withdraw these medications from the market.What were the dosages and length of use of the medications in the studies?
In the patients who have been reported to MedWatch, the average age was 44.9 years but a range in age from 22 to 67. The average weight was 200 lbs. The average dose of fenfluramine was 56 mg/day with a range of 10 to 120 mg per day. The average duration of treatment was 11.9 months but with a range of as little as 1 month and as long as 39 months.In five separate studies undertaken in asymptomatic individuals, the doses of fenfluramine were between 20 and 60 mg per day with a length of treatment of 6 to 24 months. Of note is that the incidence of cardiac valvular lesions in the asymptomatic patients was remarkably similar in all 5 centers (the incidence in the center that studied individuals after being on medication for 6 months was about the same as the center that tested individuals after being on the meds 24 months).
What were the symptoms?
In the patients that were reported to MedWatch, 61% had shortness of breath while 24% were asymptomatic but were noted to have a new heart murmur (unusual heart sound) during physical examination. 15% of the patients were found by routine screening with echocardiograms. As noted above, in the 5 studies that prompted the recall, none of the patients exhibited any symptoms.Should I be concerned?
Yes. You must stop your medications and seek medical advice as soon as possible. Remember, the preliminary finding are that over 30% of asymptomatic individuals who have used these medications are afflicted. If you do have leaky heart valves, your heart must work harder than usual to pump the blood through your body. This may result in premature heart failure or other heart problems.What should I do?
You must speak to your treating physician. Everybody taking these medications should be tapered-off as recommended by their treating physician. In the past, it was generally recommended that individuals be tapered-off over a two week period of time however, faster tapering regimes are now being proposed. It is possible that your physician may request an echocardiogram be performed to assess the heart valves. This test is non-invasive (doesn't cause any discomfort) and involves an oil being placed on your chest while a probe is pressed against your chest wall. The probe sends sound waves into your heart (which does NOT cause any damage) which results in a detailed picture of your heart being obtained.If I do have valvular damage, what will happen to me in the future?
In the years that have passed since the recall, it appears that about 10% of individuals with heart valve abnormalities have the abnormalities resolve on their own. In most people, the condition appears to stabilize but in some, leakage of the valves does worsen. If you do have heart valve abnormalities, you probably should receive antibiotics prior to any dental, urologic, or gynecologic procedure to prevent infection of the heart valves since these procedures can increase the chances of bacteria getting into your bloodstream. You will definitely need long term medical follow-up. You must discuss this with your treating physician. <Last modified: August 2001.
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Michael D. Myers M.D. Inc.
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The above information is for general purposes only and should not be construed as definitive or binding medical advice. Because each person is medically different, individuals should consult their own personal physicians for specific information and/or treatment recommendations.