Fenfluramine

Fenfluramine is a drug that was part of the serotonin, a chemical that regulates mood, appetite and other functions. Fenfluramine causes the release of serotonin by disrupting vesicular storage of the neurotransmitter, and reversing serotonin transporter function.^[1] The end result is a feeling of fullness and loss of appetite.

The drug was withdrawn from the U.S. market in 1997 after reports of heart valve disease and pulmonary hypertension, including a condition known as cardiac fibrosis. After the US withdrawal of fenfluramine, it was also withdrawn from other markets around the world.

The distinctive valvular abnormality seen with fenfluramine is a thickening of the leaflet and chordae tendinae. Roth^[2] suggested a mechanism by which fenfluramine damaged the valves. Heart valves also have serotonin receptors, which regulate their growth. He reported that fenfluramine and its active metabolite norfenfluramine stimulated the serotonin receptors 5-hydroxytryptamine (5-HT). In particular norfenfluramine is a potent agonist (stimulant) of 5-HT_2B receptors. These receptors are plentiful in human cardiac valves and appear to be essential for normal cardiac development. Roth suggested that the mechanism by which fenfluramine causes damage is through inappropriately stimulating the valve cells to divide. This valve damage is found in other drugs that act on 5-HT_2B receptors.

References

1. ^ Nestler, Eric J. "Molecular Neuropharmacology: A Foundation for Clinical Neuroscience" McGraw-Hill, 2001.
2. ^ Roth, B Drugs and Valvular Heart Disease. N Engl J Med 2007;356:6 PMID 17202450