SMC approves mexiletine hydrochloride for adults with non-dystrophic myotonic disorders

The Scottish Medicines Consortium (SMC) has approved the drug mexiletine hydrochloride (also known as NaMuscla) to treat symptoms of muscle stiffness in adults with non-dystrophic myotonic disorders.

Muscular Dystrophy UK welcomes today’s development. It means adult patients in Scotland will be able to access the treatment on the NHS if their healthcare professional thinks it is right for them.

What does the drug help with and how does it work?

Non-dystrophic myotonias are an extremely rare group of muscle disorders in which voluntary muscles are slow to relax after movement. This problem occurs intermittently, though often on a daily basis.

These disorders cause muscle stiffness (myotonia), pain, weakness and fatigue. They do not cause muscle wasting but can reduce mobility and the ability to complete daily activities.

Mexiletine hydrochloride was found to significantly improve muscle stiffness when compared with placebo in a phase III clinical study.

What was Muscular Dystrophy UK’s role in securing the treatment?

We provided the patient voice in the initial drug review and also submitted evidence to the SMC.

As well as this, MDUK attended a Patient and Clinician Engagement (PACE) meeting ahead of the SMC’s New Drugs Committee meeting.

Catherine Woodhead, CEO of MDUK, said:

We are delighted that the SMC has approved the use of mexiletine hydrochloride (NaMuscla) for adult patients with non-dystrophic myotonic disorders.

Adults living with the condition have told us first-hand how much pain and disruption muscle stiffness causes them each day, but that symptoms improve when taking the drug.

We hope for further approval of mexiletine hydrochloride across the UK to help more people living with non-dystrophic myotonic conditions.

What does today’s development mean for patients in England?

MDUK hopes to see wider availability of the drug across the rest of the UK.

Mexiletine hydrochloride is undergoing appraisal by NICE in England. MDUK has been formally involved in this process as a patient expert and will share any developments as soon as we are able to.


MDUK advises adult patients in Scotland who believe they may be eligible for treatment to contact their physician.