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Rebecca Voelker
JAMA contributor

JAMA. 1998;280:1041.

	Since this article does not have an abstract, we have provided the first 150 words of the full text and any section headings.

Outdated drug labeling has been blamed for the ill-fated coupling of fenfluramine and phentermine as an antiobesity treatment that eventually was linked with primary pulmonary hypertension and heart valve lesions.

Researchers from the Massachusetts Institute of Technology and the Massachusetts College of Pharmacy and Allied Health Sciences have reported that, although many physicians and pharmacists who prescribed and dispensed the combination were unaware of it, phentermine is a monoamine oxidase (MAO) inhibitor. Because MAO destroys serotonin in the body and fenfluramine stops plasma serotonin from being taken up into platelets, the popular "fen-phen" combination virtually wiped out the body's ability to control the amount of serotonin in blood plasma. Excess serotonin has been found to damage blood vessels and heart valves.

The researchers said phentermine's ability to inhibit MAO had been demonstrated in the 1970s, after its drug label information had been negotiated between the manufacturer and the . . . [Full Text of this Article]