Recommendations of an expert group for the cardiac assessment of non-dystrophic myotonia adult patients treated with mexiletine

Mexiletine (NaMuscla™) is indicated for the symptomatic treatment of myotonia in adults with non-dystrophic myotonia. A cardiac assessment is required as mexiletine may have a pro-arrhythmic effect. Long-term safety data supporting the use of mexiletine in patients with non-dystrophic myotonia combined with the extensive clinical experience of an expert group resulted in creation of an algorithm for cardiac monitoring of patients treated with mexiletine. To define the treatment algorithm, several expert workshops including three neurologists, five cardiologists from different French neuromuscular reference centers and one pharmacologist from Italy were set up. These workshops aimed to define the screening and surveillance tools required to ensure the safe use of mexiletine in patients. The recommendations are based on the summary of product characteristics (SmPC), a review of the literature on the safety of mexiletine-treated patients with non-dystrophic myotonia, and the expertise of the authors. The expert group concluded that the cardiac safety profile of mexiletine in these patients appears to be similar to that in the general population. Therefore, patients with non-dystrophic myotonia treated with mexiletine should be monitored as per any patient with cardiac problems who are prescribed a class 1b anti-arrhythmic.