Mediator (benfluorex), widely prescribed as an appetite suppressant, is believed to have caused over 500 deaths by heart valve failure.
The drug was withdrawn in France a decade after its withdrawal on safety grounds in Spain, Italy and the US.
Servier is accused of misleading French doctors about the risks of Mediator, whose prescription was supported by a government subsidy.
In addition to the criminal charges, several hundred civil plaintiffs are seeking damages of €100,000 each.
Servier’s President Jacques Servier, aged 90, and four other executives risk prison sentences of up to four years.
A second French trial, dealing with allegations of negligence and corruption, may follow.
Mediator, originally developed as a diabetes drug, was taken by up to 5 million people in France between 1976 and 2009 to assist weight loss.
The alleged failure of the French healthcare regulator to investigate the drug’s risks has prompted comparisons with the PIP implant scandal.
As with that case, the Mediator scandal has prompted questions about safety regulation at EU level.
Lawyer Charles Joseph Oudin commented: “Servier let people use a toxic product for years. There is no debate about it.”