The recommended starting dose of mexiletine is 167 mg daily (1 capsule per day, each capsule contains mexiletine hydrochloride corresponding to 166.62 mg mexiletine). 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.
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 (see contraindications in section 4.3 and warning in section 4.4 of full SmPC which can be downloaded here ).
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) (see sections 4.3 and 4.4 of full SmPC which can be downloaded here).
Experience with mexiletine in patients with myotonic disorders aged > 65 years is limited. Based on the pharmacokinetic properties of mexiletine, no dosage adjustment is required in patients aged 65 years and over.
Mexiletine should be used with caution in patients with mild or moderate hepatic impairment. In these patients, it is recommended that the dose should only be increased after at least 2 weeks of treatment.
Mexiletine should not be used in patients with severe hepatic impairment (see section 4.4 of full SmPC which can be downloaded here).
No dosage 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 (see section 4.4 of full SmPC which can be downloaded here).
The safety and efficacy of mexiletine in children and adolescents aged 0 to 18 years have not been established. No data are available.
Poor and extensive CYP2D6 metabolisers
Patients who are CYP2D6 poor metabolisers may exhibit higher mexiletine blood levels (see section 5.2 of full SmPC which can be downloaded here). A period of at least 7 days before dose increase must be respected to ensure that steady-state levels are reached, irrespective of the patient’s CYP450 polymorphism.
Method of administration
The capsules should be swallowed with water, avoiding the supine position. In case of digestive intolerance, capsules should be taken during a meal.
From SmPC version 1.3.1 – 6.6
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