Dexfenfluramine Pondimin

On September 15,1997, FDA asked the manufacturers of dexfenfluramine (Redux manufactured for Intemeuron Pharmaceuticals by Wyeth-Ayerst) and fenfluramine (Pondimin Wyeth-Ayerst) to voluntarily withdraw both treatments from the market because of findings that indicate approximately 30% of patients taking the combined drugs had abnormal echocardiograms, even if they had no symptoms. Both companies agreed. FDA is not requesting the withdrawal of phentermine, the third widely used medication for obesity. 

Off-label use during the 1990s became an issue after doctors in the United States and other countries began prescribing fenfluramine (Pondimin) or dexfenfluramine (Redux) in combination with phentermine. The combinations known informally as fen-phen (sometimes also written as phen-fen ) or fen-dex had not been approved by the FDA, a process that involves research and hearings. 

Fenfluramine (approved in 1973, withdrawn in 1997) and phentermine (appetite suppressant approved in 1959 and still available). Wyeth-Ayerst Laboratories, a subsidiary of American Home Products Corp. of Madison, New Jersey, manufactured and marketed fenfluramine under the brand name Pondimin. Wyeth-Ayerst also marketed Redux (dexfenfluramine), which was manufactured for Interneuron Pharmaceuticals. See http //www.fda.gov/cder/news/phen/fenphenpr81597.htm... 

New pharmacological treatments have been developed for the treatment of obesity. These include the combination of phentermine and fenfluramine (phen-fen) and, alternatively, dexfenfluramine (Redux). Phentermine (Fastin, lonamin) is a stimulant and fenfluramine (Pondimin) is a serotonin agonist. In combination they have persistent appetite suppression and weight loss effects. These medications can cause anxiety and insomnia and must be used with extreme caution if taken with antidepressants, especially SSRIs. Dexfenfluramine works similarly, but avoids the side effect of increased anxiety, and instead tends to cause diarrhea, dry mouth, and somnolence. There have also been reports of pulmonary hypertension, a potentially fatal condition, especially when taken for longer than three months. Some researchers (Ricuarte et al. 1991 McCann et al. 1994) have expressed concern because rats given these medications showed evidence of neuronal toxicity. Thus, they are effective medications, but must be used with caution. 

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