(HealthDay News) — There is preliminary evidence that mexiletine is effective for patients with rare nondystrophic myotonias (NDMs), according to a study published in the Oct 3 issue of the Journal of the American Medical Association.

Jeffrey M. Statland, MD, from the University of Rochester Medical Center in New York, and colleagues conducted an international two-period crossover study in which 59 patients with NDMs were given oral 200mg mexiletine or placebo capsules three times daily for four weeks. Following a one-week washout period, patients were treated with the opposite intervention for four weeks.

The researchers observed a significant improvement on a patient-reported severity score of stiffness recorded on an interactive voice response diary with mexiletine, with the difference significant for each of the two treatment periods. There was also a significant improvement with mexiletine on the Individualized Neuromuscular Quality of Life summary quality-of-life score (14 for mexiletine vs. 16.7 for placebo), and on clinical examination, there was significantly decreased handgrip myotonia noted (0.164 seconds for mexiletine versus 0.494 seconds for placebo). Gastrointestinal adverse effects were the most common (nine mexiletine and one placebo) and one participant in each group experienced transient cardiac effects that did not require stopping the study.

“In this preliminary study of patients with NDMs, the use of mexiletine compared with placebo resulted in improved patient-reported stiffness over four weeks of treatment, despite some concern about the maintenance of blinding,” Statland and colleagues conclude.

Several authors disclosed financial ties to the pharmaceutical industry.

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