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Fen-Phen Damage Long-Lasting

Nov 6, 2008 | Parker Waichman Alonso LLP

The dangerous diet drug fenfluramine, an ingredient in Fen-Phen, may continue to damage the heart years after a patient stops taking it, according to a study published online today in BMC Medicine.  The study has shown  that people who stopped using Fen-Phen eleven years ago had damaged heart valves up to seven years later.

The study, conducted by researchers at the Central Utah Clinic, involved both fenfluramine and dexfenfluramine, another diet drug that is closely related to fenfluramine.  The Food & Drug Administration (FDA)  ordered fenfluramine and dexfenfluramine off the market in September 1997 after those drugs were linked to heart valve problems. Since its withdrawal, tens of thousands of lawsuits have been filed against the maker of fenfluramine by people injured by the drug.

This is the largest study to examine duration of exposure to the drug and the first to estimate the incidence of heart valve surgery among prior users. The researchers looked at 5,743 former users of fenfluramine and/or dexfenfluramine.  The patients were seen by doctors at the Central Utah Clinic between July 1997 and February 2004.  Each patient got an echocardiogram and 1,020 patients got two or more echocardiograms 30 months apart, on average.

When the study started, nearly 20% of the women and almost 12% of the men had at least mild regurgitation through the aortic valve or moderate regurgitation through the mitral valve.  Women, and people  who used the drugs the longest were most likely to have such problems.

Follow-up echocardiograms showed that aortic and mitral regurgitation usually stayed about the same or worsened, but improved in some cases. Thirty-eight patients -- less than 1% -- got heart valve surgery. Such surgery wasn't common, but it was more common than in the general public, and in 25 cases, heart valve damage was linked to the drugs.

"We found clear evidence for a strong, graded association between duration of exposure to fenfluramines and prevalence of aortic regurgitation and for mild or greater mitral and tricuspid regurgitation," lead researcher Charles Dahl, told Science Daily.