Treatment strategies in non-dystrophic myotonias are based on selective case reports,
clinical experience and theoretical benefit. Presently, the most promising antimyotonic
medication is mexiletine (MEX) but its manufacturing was stopped. The proposed randomized,
double-blind, placebo-controlled, crossover trial is designed to:
1. study the safety and efficacy of mexiletine for the treatment of non-dystrophic
myotonias
2. validate electromyographic tests as a standardized outcome measure of myotonia
3. assess the reliability and validity of a new clinical rating scale for myotonia