Aminorex to Fen/Phen: An Epidemic Foretold

To the Editor: I read the article by Alfred P. Fishman1 with interest. He refers to “an unexpected outbreak of valvular heart disease related to the use of anorectic agents” and implicates the combination of fenfluramine and phentermine as the cause of this outbreak. He states that the fen/phen combination “enables high levels of circulating serotonin to reach the left side of the heart” and, in commenting on the similarity between the cardiac valvular lesions in patients taking fen/phen and carcinoid syndrome, he states that “in both instances, the lesions are attributable to inordinately high concentrations of serotonin in the blood.” He explains the disparity between the presence of left-sided lesions in fen/phen patients and their absence in patients with carcinoid syndrome by a hypothetical diagram suggesting that both fenfluramine and phentermine impair the pulmonary clearance of serotonin and permit “abnormally high concentrations of serotonin to reach the left side of the heart.” Although there may have been an outbreak of uncontrolled research papers and abstracts (at the …