Mexiletine for treating the symptoms of myotonia in non-dystrophic myotonic disorders

1.1 Mexiletine (Namuscla) is recommended, within its marketing authorisation, as an option for treating the symptoms of myotonia in adults with non-dystrophic myotonic disorders. It is recommended only if the company provides mexiletine (Namuscla) according to the commercial arrangement.

Why the committee made these recommendations

Treatments for the symptoms of myotonia in adults with non-dystrophic myotonic disorders already include imported mexiletine (which is not licensed in the UK). Other sodium channel blockers are used if mexiletine is not suitable. NICE's remit for this appraisal is to appraise Namuscla, the only brand of mexiletine with a UK marketing authorisation.

Clinical trial evidence suggests that mexiletine is better than placebo at reducing the symptoms of myotonia. But the trial did not compare mexiletine with other sodium channel blockers. Also, a higher dose of mexiletine was used in the clinical trial than people would normally have in the NHS.

The economic model does not compare mexiletine with other sodium channel blockers that are used in the NHS. Because of this, mexiletine's clinical benefit compared with these medicines is uncertain. However, the cost-effectiveness estimates for mexiletine compared with best supportive care are within the range that NICE considers a cost-effective use of NHS resources. It is uncertain if they would exceed this range when compared with other sodium channel blockers. Therefore, mexiletine (Namuscla) is recommended.