Source: European Medicines Agency (EU) Revision Year: 2026 Publisher: Lupin Europe GmbH, Hanauer Landstraße 139-143, 60314, Frankfurt am Main, Germany
Namuscla is indicated for the symptomatic treatment of myotonia in children aged 6 to 11 years weighing at least 20 kg, adolescents aged 12 to 17 years and adult patients ≥18 years with non-dystrophic myotonic disorders.
Before starting mexiletine treatment,
The recommended starting dose of mexiletine is 167 mg daily (1 capsule per day). 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 (3 capsules per day).
Maintenance treatment is between 167 mg – 500 mg daily (1 to 3 capsules per day), according to the intensity of symptoms and the clinical response, taken regularly throughout the day as required.
The dose should not exceed 500 mg/day. Regular reassessment should be implemented: discontinue long-term treatment in a patient not responding or not experiencing benefit of the treatment.
In paediatric patients, the recommended dose is dependent on body weight (Table 1):
Table 1. Recommended doses in paediatric patients:
| Body weight (kg) | Once daily (morning) | Twice daily (morning and evening) | Three times daily (morning, afternoon and evening) | Maximum total dailydose |
| 20-30 kg | 62 mg (1 x 62 mg) | 124 mg (2 x 62 mg) | 186 mg (3 x 62 mg) | ≈187 mg/day |
| 30-40 kg | 83 mg (1 x 83 mg) | 166 mg (2 x 83 mg) | 249 mg (3 x 83 mg) | ≈250 mg/day |
| Alternative: 248 mg (4 × 62 mg) | ||||
| 40-60 kg | 124 mg (2 x 62 mg) | 248 mg (4 x 62 mg) | 372 mg (6 x 62 mg) | ≈375 mg/day |
| ≥60 kg | 167 mg (1 x 167 mg or 2 x 83 mg) | 334 mg (2 x 167 mg or 4 x 83 mg) | 501 mg (3 x 167 mg or 6 x 83 mg) | 500 mg/day |
In case of modification of the mexiletine dose, or if medicinal products likely to affect cardiac conduction are co-administered with mexiletine, patients should be closely monitored by ECG (especially patients with conduction anomalies) (see sections 4.3, 4.4 and 4.5).
Experience with mexiletine in patients with myotonic disorders aged ≥65 years is limited. Based on the pharmacokinetic properties of mexiletine, no dose adjustment is required in patients aged 65 years and over.
Mexiletine should be used with caution in patients with mild (5-6 Child-Pugh score) or moderate (7-9 Child-Pugh score) hepatic impairment. In these patients, it is recommended that the dose should only be increased after at least 2 weeks of treatment.
The experience with mexiletine in patients with severe hepatic impairment is limited. Therefore, mexiletine should not be used in this patient population.
No dose adjustment is considered necessary in patients with mild or moderate renal impairment. The experience with mexiletine in patients with severe renal impairment is limited. Therefore, the use of mexiletine is not recommended in this patient population.
Children less than 6 years of age The safety and efficacy of mexiletine in children aged below 6 years or weighing below 20 kg have not yet been established. No data are available.
Oral use.
The whole capsules should be swallowed with water, avoiding the supine position. In case of digestive intolerance, capsules should be taken during a meal.
The safety and efficacy of opening the capsules or administering the contents by other routes have not been established. Studies are being conducted to assess suitability of alternative administration methods. For patients who are unable to swallow capsules, healthcare professionals should decide on appropriate administration based on clinical judgement.
Fatal outcomes have been reported for acute overdoses at 4.4 g of mexiletine hydrochloride ingestion but survival has also been reported following acute overdose of approximately 4 g of oral mexiletine hydrochloride.
The symptoms of mexiletine overdose include neurological disorders (paraesthesia, confusion, hallucination, seizure) and cardiac disorders (sinus bradycardia, hypotension, collapse, and in extreme cases, cardiac arrest).
The treatment is mainly symptomatic. The seriousness of the symptoms may require hospital supervision. In case of bradycardia with hypotension, intravenous atropine should be used. In case of seizure, benzodiazepines should be used.
3 years.
Do not store above 30°C.
Store in the original package in order to protect from moisture.
Namuscla hard capsules are packed in Aluminium/PVC/PVDC blisters containing 30, 50, 100, 200 or 300 capsules in a carton.
Not all pack sizes may be marketed.
Any unused medicinal product or waste material should be disposed of in accordance with local requirements.
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