Phentermine To Blame for Fen-Phen Side Effects?

An article in The Wall Street Journal reports that treatment withphentermine in combination with the antidepressant Prozac (fluoxetine) may result in cardiac side effects as serious as those seen with the phentermine-Pondimin (fenfluramine) and phentermine-Redux (dexfenfluramine) combinations. This was the finding that led to the recall of the drugs, both sold by American Home Products, last year (Marketletters Passim). Since the recall, the new trend in diet aid medication is for prescribing Prozac with phentermine instead. The drug combinations are taken by dieters to modulate appetite.

The occurrence of heart valve lesions seen in "fen-phen" patients is due to the phentermine, according to Massachusets Institute of Technology's Richard Wurtman, who has researched the compound's mode of action. He found that phentermine acts as a monoamine oxidase inhibitor, resulting in excess serotonin in the blood stream. Excess blood serotonin would normally be removed by the platelets, but Redux and Pondimin prevent this action, resulting in excessive levels of blood serotonin, which narrow blood vessels and damages heart valves. According to Dr Wurtman's colleague Tim Maher, this accounts for the sudden incidence of these side effects when the drugs are combined.

Criticism From Drugmakers Dr Wurtman's research has received criticism from the makers of phentermine, Medeva Pharmaceuticals and SmithKline Beecham, which claim he has a conflict of interest given his financial stake in Interneuron Pharmaceuticals which developed the recalled Redux. Dr Wurtman was a co-founder of Interneuron and holds significant equity. The phentermine drugmakers are quick to discredit the research as "blatant unsupported advocacy," and "incorrect" and "totally misleading."