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 placeboLe placebo est un produit dont la présentation est identique à celle d’un médicament, mais qui ne contient pas de principe actif. Dans un essai clinique, un placebo est utilisé pour mesurer l’action réelle du médicament testé, en comparant les effets du médicament testé contenant le principe actif et ceux du 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.