Created by FindLaw's team of legal writers and editors | Last reviewed December 21, 2016
Fen-phen is the common name of a combination of two drugs: fenfluramine (fen) and phentermine (phen). A similar drug "dexfen-phen" is a combination of dexfenfluramine and phentermine. Both fenfluramine and phentermine were approved by the FDA as appetite suppressing drugs for short-term weight loss for obese people. Dexfenfluramine was the first appetite-suppressing drug for long-term obesity treatment. The FDA approved phentermine in 1959, fenfluramine in 1973, and dexfenfluramine (Redux) in 1996.
In the 1990s, some doctors prescribed fenfluramine or dexfenfluramine in combination with phentermine for long-term use in weight loss or diet programs, often for non-obese individuals. Prescribing drugs for use in ways other than what was approved by the FDA is called "off-label use." No research or studies were submitted to the FDA demonstrating either the safety or effectiveness of fen-phen or in other combos, so no combo was approved by the FDA.
For more information, see the Fen-Phen FAQs.
Fenfluramine and Dexfenfluramine: Withdrawal from Market
In September 1997, the FDA asked the manufacturers of fenfluramine and dexfenfluramine to voluntarily withdraw both products from the market. Dexfenfluramine was manufactured for Interneuron Pharmaceuticals and marketed under the name "Redux" by Wyeth-Ayerst Laboratories, a subsidiary of American Home Products Corp. of Madison, N.J., which also manufactured and marketed fenfluramine under the brand name "Pondimin." Both companies agreed to voluntarily withdraw their drugs. The FDA didn’t request the withdrawal of phentermine, the third widely used medication for obesity.
The FDA request for withdrawal of these diet pills from the market came after users of fen-phen had echocardiogram testing done that suggested fenfluramine and dexfenfluramine were the likely cause of heart valve problems. On September 15, 1997, FDA recommended that patients using either of these products stop taking them, and advised patients to contact their doctors to discuss their treatment.
Studies Reveal Heart Valve Problems
In July 1997, researchers at the Mayo Clinic reported 24 cases of rare valvular disease in women who took fen-phen. Later, the FDA received 66 additional reports of heart valve disease associated mainly with "fen-phen." There were also reports of cases seen in patients taking only fenfluramine or dexfenfluramine.
The heart contains 4 major valves that regulate the flow of blood through the heart and to the lungs and general circulation. Disease may cause excessive tightness (stenosis) or leakiness (regurgitation) of the valves. Leakiness was the valve problem associated with fenfluramine and dexfenfluramine. Valvular damage may ultimately produce severe heart or lung disease.
Heart Risks for Fenfluramine and Dexfenfluramine Users
Fenfluramine and dexfenfluramine users or former users may have changes in their heart valves that cause leakiness and the backflow of blood. If this is severe, the heart has to work harder, which may cause heart problems.
A person may have no symptoms, but still have a heart valve problem. The doctor may hear a new heart murmur (abnormal sound as the blood flows over a valve), or the changes may be detected with a painless, non-invasive special heart test called an echocardiogram. An echocardiogram is usually performed by a cardiologist. If it’s a serious heart valve problem, the person may have symptoms such as shortness of breath, excessive tiredness, chest pain, fainting, and swelling of the legs.
After the market withdrawal of fenfluramine and dexfenfluramine, hundreds of former fen-phen patients have sued the drugs' manufacturers. One national class action suit settled in January 2002. If you or a loved one was injured as a result of fen-phen or other diet pill use, your rights may be impacted by other legal proceedings related to Fen-phen. However, you still may be able to sue for your fen-phen injuries, especially if your health problems were only recently discovered.
To understand and protect your rights, contact an experienced attorney. For more information on an attorney's role in a Dangerous Drugs case, see the Get Legal Help with a Defect Product Injury article.
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