Euthyrox has been prescribed to treat thyroid conditions –including hypothyroidism – for decades and is used by around three million French citizens.
In 2012, French regulator ANSM asked Merck to reformulate the drug to ensure its active ingredient – levothyroxine – is more stable over the product's shelf life. The revamped pill – which contains the excipient mannitol rather than lactose – was approved by ANSM last September and launched in France in March this year.
In the months since, the new formulation has been the subject of 9,000 adverse event reports according to ANSM, which told us there had been a surge in submissions by patients and doctors to its online portal since August.
“As of August 16, 2017 there was an increase in the total number of reports. This increase was progressive until reaching a peak on August 23, 2017 with 1,200 reports, all medicines combined”
ANSM added “these reports are probably due to Euthyrox” going on to say that “cumulatively, it is estimated to September 9 that 9 000 reports related to Euthyrox during the period.”
The regulator is due to release a full report next month.
But despite the increase in adverse event reports by Euthyrox users, ANSM is confident the reformulated drug is safe.
The agency told us “The new formula ensures a stable quantity of active substance which is more constant from one lot to another or within the same batch and throughout the shelf life of the product than the old formulation. The quality of the drug has therefore been improved.
It added that: “The active substance of the novel formula is unchanged in its nature and in its dosage.”
This echoed comments by French health minister Agnes Buzyn, who told the press (in French) on Monday the problem was how information about the new formulation had been communicated.
Buzyn said: "There is no fraud, there is no conspiracy, there is no error, there was a problem of informing the patients (...) and therefore the patients were found surprised by a formulation that had changed and that for some gave side effects” according to Le Figaro.
"Many of these side effects are related to difficulties in correctly re-ordering Levothyrox but they fade when the treatment is well dosed" she said.
The comments came days after ANSM moved to restrict access to liquid formulations of levothyroxine-based products to patients for whom solid dose formulations are not appropriate (here in French).
No safety or efficacy change
Merck said it is confident of the safety and efficacy of the new formulation, also pointing out that the drug’s active pharmaceutical ingredient (API) had not been impacted by the changes to the excipients.
However, the German drug firm stressed it is monitoring the situation, telling us “We take patients’ concerns and the petition in France regarding the new formulation of Euthyrox very seriously, and are collaborating closely with the local regulatory body to monitor all reports.
“All reported side effects are carefully assessed. For the overwhelming majority of the three million patients treated with Euthyrox, the transition from the old to the new formulation has been successful without any complaints.