Fen-phen was an anti-obesity medication (an anorectic) which consisted of two drugs: fenfluramine and phentermine. Fenfluramine, and later, a related drug, dexfenfluramine, was marketed by American Home Products, now known as Wyeth.
After reports of valvular heart disease and pulmonary hypertension, primarily in women who had been undergoing treatment with Fen-phen, the Food and Drug Administration (FDA) requested its withdrawal from the market in September 1997.
The action was based on findings from doctors who had evaluated patients taking these two drugs with echocardiograms, a special procedure that can test the functioning of heart valves. These findings indicated that approximately 30 percent of patients who were evaluated had abnormal echocardiograms, even though they had no symptoms. This percentage of abnormal test results was much higher than would be expected from a comparatively-sized sample of the population who had not been exposed to either fenfluramine or dexfenfluramine.
In July 1997, researchers at the Mayo Clinic and Mayo Foundation reported 24 cases of rare valvular disease in women who took the Fen-phen combination therapy. The FDA alerted medical doctors that it had received nine additional reports of the same type, and requested all health care professionals to report any such cases to the agency’s MedWatch program, or to their respective pharmaceutical manufacturers.
The FDA subsequently received 66 additional reports of heart valve disease, all primarily associated with Fen-phen. There were also reports of documented heart-valve problems in patients taking only either fenfluramine or dexfenfluramine. The FDA requested that the manufacturers of fenfluramine and dexfenfluramine stress the potential risk to the heart in the drugs' labeling and in patient package inserts. As of 1997, the FDA was continuing to receive reports of cardiac valvular disease in persons who have taken these drugs. This valvular disease typically involves the aortic and mitral valves.
As of 2004, Fen-phen is no longer widely available. In April 2005, American Lawyer magazine ran a cover story on the Fen-phen mass tort crisis, reporting that more than 50,000 product liability lawsuits had been filed by alleged Fen-phen victims. Estimates of total liability run as high as $14 billion.