NICE has published draft guidance which recommends a rebranded form of the drug mexiletine (Namuscla), for treating the symptoms of myotonia in adults with non-dystrophic myotonic disorders (NDM). It is estimated that around 250 people will be eligible to have Namuscla.
NICE has been asked to appraise Namuscla, as it is the only product for treating this condition with a UK marketing authorisation. It is currently available through an agreement between NHS England, and NHS Improvement and the company. Before Namuscla was licensed, treatments included imported mexiletine (which was not licensed in the UK), and other sodium channel blockers.
Clinical trial evidence has shown that Namuscla is more effective than placebo at reducing the symptoms of myotonia, but the trial did not compare Namuscla with other sodium channel blockers, such as lamotrigine, carbamazepine, acetazolamide, flecainide, and phenytoin, used in the NHS for treating the condition.
A higher dose of Namuscla was used in the clinical trial than people would normally have in the NHS, and the size of the clinical benefit is also uncertain. Despite these limitations, Namuscla is a cost-effective use of NHS resources, and it is recommended for routine commissioning.
NDM denotes a group of rare genetic disorders which affect the muscles. The most common symptom is myotonia, which is a delay in muscle relaxation, and can cause muscular locking and stiffness, pain, lack of sleep, and falling. Myotonia can severely impair the quality of life in sufferers, and can lead to difficulty carrying out daily tasks such as lifting, climbing stairs, or bathing.
Sodium channel blockers, including mexiletine, have been used off-label for many years to treat NDM. Myotonic disorders are rare, and Namuscla was designated an ‘orphan medicine’ (a medicine used in rare diseases) in 2014.
