Myotonia in non-dystrophic myotonic disorders

Indication for Mexiletine

Population group: Suitable for both men and women, only adults (18 years old or older)

Mexiletine is indicated for the symptomatic treatment of myotonia in adult patients with non-dystrophic myotonic disorders.

For this indication, competent medicine agencies globally authorize below treatments:

167-500 mg once daily

Route of admnistration


Defined daily dose

167 - 500 mg

Dosage regimen

From 167 To 500 mg once every day

Loading dose

167 mg

Detailed description

The recommended starting dose of mexiletine is 167 mg daily. After at least 1 week of treatment, based on the clinical response, the daily dose can be increased to 333 mg daily (2 capsules per day). After at least 1 further week of treatment, based on clinical response, dose can be further increased to 500 mg daily. Maintenance treatment is between 167 mg–500 mg daily, according to the intensity of symptoms and the clinical response, taken regularly throughout the day.

The dose should not exceed 500 mg/day. Regular reassessment should be implemented, not to continue long-term treatment in a patient not responding or not experiencing benefit of the treatment. Before starting mexiletine treatment, detailed and careful cardiac evaluation should be carried out; throughout treatment with mexiletine, cardiac monitoring needs to be continued and adapted as a function of the heart condition of the patient.

Patients with cardiac disorders

In case of modification of the mexiletine dose, or if medicinal products susceptible to affect cardiac conduction are co-administered with mexiletine, patients should be closely monitored by ECG (especially patients with conduction anomalies).

Active ingredient

Mexiletine blocks sodium channels with a stronger potency in situations of excessive burst of action potentials (use-dependent block) and/or prolonged depolarization (voltage-dependent block), as occurring in diseased tissues, rather than on physiological excitability (resting or tonic block). Mexiletine is, therefore, mostly active on muscle fibres subject to repeated discharges (such as skeletal muscles). It improves myotonic symptoms by decreasing muscle stiffness through reduction of the delay of muscle relaxation.

Read more about Mexiletine

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