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Dieting Drug Redux® May Cause Brain Damage; Related Weight Loss Drugs Linked to Heart Ailments


July 1997

Dexfenfluramine, also known as Redux®, a popular dieting aid, may cause brain damage. Several prominent neurotoxicologists claim that even low doses of the drug can damage serotonin-producing neurons, and they say that the Food and Drug Administration (FDA) is hiding this information (Kurt Kleiner, "Secrecy row over slimmer's drug," New Scientist, June 28, 1997).

Redux® was approved by the FDA last year. It works to regulate appetite by increasing the brain's level of serotonin. Tests have been performed on animals that show that a dose only twice the recommended dosage to reduce weight loss, can cause damage to serotonin-producing neurons. However, this effect has not been confirmed in humans.

The FDA, when granting approval for Wyeth-Ayerst Laboratories to market the drug, mandated a follow-up study to check for brain damage in users, in response to concerns raised by several scientists. The trial has not yet taken place.

On July 8, physicians at the Mayo Clinic in Rochester, Minnesota reported that fenfluramine and phentermine, known in combination as "fen/phen," may cause a rare, severe form of heart valve disease. Their report will appear in the New England Journal of Medicine in late August.

The FDA plans to contact physicians to inform them of the possible problems and to ask of possible heart valve cases involving their patients who take the prescription diet drugs. However, the FDA has no immediate plans to withdraw the drugs or to add warnings to their labels. Wyeth-Ayerst sells fenfluramine under the trade name Pondimin®. Fenfluramine is chemically closely related to Redux®, but the heart valve disease announcement did not involve Redux®.