Potential Hazard of Serotonin Syndrome Associated With Dexfenfluramine Hydrochloride (Redux)

To the Editor.  —The Food and Drug Administration recently approved labeling of dexfenfluramine hydrochloride for the long-term treatment of obesity.^1,2 Primary care physicians, not just obesity treatment specialists, will almost certainly be targets of an intense marketing campaign by the manufacturer of dexfenfluramine, since this drug purportedly represents an advance in the management of a major public health problem. However, we feel compelled to alert physicians to the hazard of serotonin syndrome^3,4 that awaits the use of dexfenfluramine within the context of contemporary psychotropic prescribing patterns.Dexfenfluramine is a nonspecific serotonin agonist that both enhances the release of serotonin from axonal terminals of presynaptic neurons and inhibits the reuptake of serotonin into these terminals, resulting in a potent increase of serotonin availability at postsynaptic receptors.⁵ The potential for serotonin syndrome exists if dexfenfluramine is taken concurrently with 1 or more of the many serotoninergic drugs that are