Phentermine-Induced Dilated Cardiomyopathy: A Case Report and Review of Literature.

Phentermine is a sympathomimetic amine with pharmacologic properties similar to amphetamines. Phentermine's mechanism of action is via stimulation of the hypothalamus, leading to norepinephrine release, which in turn leads to reduced appetite. Approved by the FDA in 1959, phentermine has long been prescribed for weight loss in patients with obesity and remains commonly used in the United States. Despite its effectiveness in suppressing appetite and promoting weight reduction, phentermine can lead to several side effects involving the cardiovascular, gastrointestinal, and endocrine systems. In the 1990s, new-onset valvulopathy and cardiomyopathy as a result of combination therapy with phentermine and fenfluramine were discovered, leading to the discontinuation of this therapy. Combination therapy with phentermine-topiramate was approved by the FDA for long-term weight loss management in 2012 and has since been a commonly prescribed treatment regimen. Aside from associated increases in both heart rate and blood pressure, major cardiovascular side effects have seldom been reported in the literature. We report a case of new-onset non-ischemic dilated cardiomyopathy and moderate to severe mitral valve regurgitation in a patient with greater than two years of exposure to phentermine-topiramate.