The now-banned diabetes and weight loss drug Mediator may have been linked to the deaths of about 500 people in the 33 years it was on the market.
France's health products safety agency has advised those who used the drug from 2006 to 2009 to see their doctor to check for possible heart valve problems.
The agency said Tuesday that about 5 million people used Mediator — the brand name for benfluorex in France — from 1976 until it was pulled off the market in 2009.
The European Medicines Agency said last year that it decided to remove benfluorex from the market because it had little effect on diabetes and might lead to a dangerous thickening of heart valves.
Benfluorex, used especially to treat weight problems among diabetics, underwent various tests over time, but it was only in 2006 that a confirmed case of heart valve problems related to its use was reported, the health safety agency said.