The Myomex trial confirms the interest of the prescription of mexiletine in non-dystrophic myotonias

The Myomex trial, conducted by the AP-HP (the Paris public hospital system) and supported by AFM-Téléthon, evaluated the efficacy and safety versus placebo of a daily dose of 600 mg of mexiletine (Namuscla®) in 25 participants, 13 of which had myotonia congenita and 12 of which had paramyotonia congenita. Their symptoms had to be sufficiently severe to justify treatment.

The results of this trial show a significant improvement versus placebo:

  • muscle rigidity score, determined by participants using a visual analogue scale, went from 71 at the start of the trial, to 16 after 18 days of treatment (-78%);
  • quality of life in its different dimensions.

A trial of Namuscla® in children and adolescents with non-dystrophic myotonias has begun.

 

Efficacy and safety of mexiletine in non-dystrophic myotonias: A randomised, double-blind, placebo-controlled, cross-over study. Vicart S, Franques J, Bouhour F et al. Neuromuscul Disord. 2021 Jun 27:S0960-8966(21)00164-4.