Fenfluramine/phentermine

The drug combination fenfluramine/phentermine, usually called fen-phen, is an anti-obesity medication that is no longer widely available. It was sold in the early 1990s, and utilized two anorectics. Fenfluramine was marketed by American Home Products (later known as Wyeth) as Pondimin, but was shown to cause potentially fatal pulmonary hypertension and heart valve problems, which eventually led to its withdrawal in 1997 and legal damages of over $13 billion.[ 1] Phentermine was not shown to have harmful effects.[ 1]

Fenfluramine acts as a serotonin releasing agent,[ 2] phentermine as primarily a norepinephrine releasing agent. Phentermine also induces the release of serotonin and dopamine, although to a far lesser extent than it induces the release of norepinephrine.[ 3]

Fenfluramine as a single drug was first introduced in the 1970s, but was not popular because it only temporarily reduced weight.[ 1] A 1984 study found a weight loss of 7.5 kg on average in 24 weeks, as compared to 4.4 kg under placebo.[ 4] It sold modestly until the 1990s, when it was combined with phentermine and heavily marketed.[ 1]

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