PARIS: France's ANSM national drug agency said it is under formal investigation on suspicion of issuing misleading information regarding German drugmaker Merck's thyroid drug Levothyrox, adding it contested the provisional charges.
"The ANSM has never denied the difficulties encountered by some patients during the changeover to the new Levothyrox formula and works each and every day for the safety and health of patients," ANSM said in a statement late on Monday.
The French Association of Thyroid Patients on Tuesday welcomed the development, but expressed disappointment that the provisional charges had not been more far-reaching.
In an earlier civil litigation, France's highest court in March upheld a ruling that ordered Merck to pay €1,000 (US$982) each to more than 3,300 people with thyroid problems in France after it changed the formula of Levothyrox in 2017.
The plaintiffs said Merck's decision to remove lactose from the drug to make it easier to handle had resulted in side effects such as memory loss, weight gain and palpitations.
A court in the French city of Marseille had in October already placed Merck under formal investigation, meaning it is treated as a formal suspect but the case may yet be dropped.
Merck said in October the investigation against it did not concern in any way the new formula for Levothyrox, but the way it provided information when changing from the old one.