 Approximately 5 million people in the United States were given fenfluramine or dexfenfluramine with or without phentermine between 1996 and 1998.In the early 1990s, French researchers reported an association of fenfluramine with primary pulmonary hypertension and dyspnea in a small sample of patients.Fenfluramine was withdrawn from the U.S. market in 1997 after reports of heart valve disease and continued findings of pulmonary hypertension, including a condition known as cardiac fibrosis.