Study Comparing Mexiletine Prolonged-Release and Immediate-Release for Treating Non-Dystrophic Myotonias

What this Trial Is About

This research investigates the safety and effectiveness of two forms of mexiletineprolonged-release PR and immediate-release IRin patients with non-dystrophic myotonias, including myotonia congenita, paramyotonia congenita, and sodium channel myotonia. This multicenter, open-label, randomized, cross-over study aims to compare these forms to better understand their effects on this condition. The study plans to enroll 24 patients, split evenly between those who are new to mexiletine treatment and those with previous treatment experience. Participants will undergo a 4-week screening followed by two 12-week treatment periods. Initially, patients will be randomly assigned to receive either mexiletine PR once daily or mexiletine IR three times daily. After a washout period of at least 7 days, they will switch to the other treatment for another 12 weeks. Different doses of mexiletine PR 167 mg, 333 mg, or 500 mg and mexiletine IR 167 mg are used to assess safety and efficacy. Throughout the study, participants will be closely monitored through patient and physician reports of adverse events, electrocardiograms ECGs, laboratory tests, physical exams, and vital signs. Efficacy will be measured using patient-reported outcomes and functional tests such as handgrip relaxation time, timed walking tests, and quality of life assessments. The main safety comparisons include heart rhythm intervals and rates, with observations continuing from baseline through week 24.

An Open-Label, Randomized, Cross-Over Study to Investigate the Efficacy and Safety of Mexiletine PR Compared to Mexiletine IR