Fen-Phen Overview
What is "Fen-Phen"?
Fen-phen refers to the use in combination of the drugs fenfluramine and phentermine. Phentermine has also been used in combination with dexfenfluramine ("dexfen-phen"). Fenfluramine ("fen") and phentermine ("phen") are prescription medications that were approved by the FDA for many years as appetite suppressants for the short-term (a few weeks) management of obesity. Phentermine was approved in 1959 and fenfluramine in 1973. Dexfenfluramine (Redux) was approved in 1996 for use as an appetite suppressant in the management of obesity.
In the 1990's, some physicians began prescribing fenfluramine or dexfenfluramine in combination with phentermine, often for extended periods of time, for use in weight loss programs. Use of drugs in ways other than described in the FDA-approved label is called "off-label use." In the case of fen-phen and dexfen-phen, no studies were presented to the FDA to demonstrate either the effectiveness or safety of the drugs taken in combination, so use of the drugs in combination never received FDA approval.
Fenfluramine and Dexfenfluramine: Withdrawal from Market
In September 1997, the FDA asked the manufacturers to voluntarily withdraw dexfenfluramine and fenfluramine 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 did not request the withdrawal of phentermine, the third widely used medication for obesity.
The FDA's withdrawal request came after echocardiogram testing of fen-phen patients suggested that fenfluramine and dexfenfluramine were the likely cause of heart valve problems (more on heart valve problems and risks to fenfluramine and dexfenfluramine users follows below).
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.
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Most content above from the U.S. Food and Drug Administration (FDA)
