Answer
Mexiletine hydrochloride preferentially blocks sodium channels in muscle fibres undergoing repeated discharges or prolonged depolarisation, reducing delayed muscle relaxation and therefore muscle stiffness in myotonia.
Sources for this answer
- Namuscla 167 mg hard capsulesLupin Healthcare (UK) Ltd · emc · SmPC §5.1 Pharmacodynamic properties · Version 3Document updated
Sources checked