Objective: The aim of our study was to evaluate the long-term efficacy and safety of
mexiletine in 112 patients affected by genetically confirmed non-dystrophic
myotonias. The study was performed at the Neurophysiologic Division of Fondazione Policlinico Universitario A. Gemelli Istituto di Ricerca e Cura a Carattere Scientifico (IRCCS), Rome and the Children's Hospital Bambino Gesù, Rome. Methods: The treatment was accepted by 59 patients according to clinical severity, individual needs, and concerns about a chronic medication. Forty-three patients were affected by recessive congenita
myotonia, 11 by
sodium channel myotonia, and five by dominant
congenital myotonia. They underwent clinical examination before and after starting
therapy, and Electromyography (EMG). A number of recessive
myotonia patients underwent a protocol of repetitive nerve stimulations, for detecting and quantifying the transitory weakness, and a modified version of the Timed Up and Go test, to document and quantify the gait impairment. Results:
Treatment duration ranged from 1 month to 20 years and the daily dosages in adults ranged between 200 and 600 mg. No patient developed
cardiac arrhythmias causing
drug discontinuation.
Mexiletine was suspended in 13 cases (22%); in three patients, affected by
Sodium Channel myotonia, because
flecainide showed better efficacy; in one patient because of a
gastric cancer antecedent treatment; in four patients because of untreatable
dyspepsia; and five patients considered the treatment not necessary. Conclusions: In our experience,
mexiletine is very useful and not expensive. We did not observe any hazarding
cardiac arrhythmias.
Dyspepsia was the most frequent dose-limiting side effect.