Abstract-Text (inkl. Referenzen)

Introduction NDMs are rare genetic channelopathies causing hyperexcitability of muscle fibres, resulting in stiffness, locked muscles and pain. Mexiletine is the only licensed symptomatic treatment of myotonia in adult patients with NDM. Long-term data in a real-world setting, to provide a proven positive risk–benefit profile for effective treatment of myotonia symptoms is needed.

Method Up to 50 adult patients will be enrolled over 2 years in 6 investigator sites. Study population consists of newly initiated patients on NaMuscla® (mexiletine) and patients already on NaMuscla® at enrolment.

Data will be captured in eCRF, through physician assessment and patient self-assessment tools. Data collection is at 12, 24 and 36 months from enrolment, follow-up calls at 6, 18 and 30 months. Total study duration is 5 years with interim analyses at 1 and 3 years.

Primary endpoints are treatment-emergent AEs, including serious AEs and dose reduction or treatment discontinuation due to AEs. Secondary safety endpoints include patients with AEs, SAEs or AEs of special interest; Secondary efficacy endpoints include changes in VAS, MBS and INQoL questionnaire scores from baseline; and clinical myotonia evaluation over time. Limitations include selection bias; no control group; and clinical practice differences between countries.

Discussion This study will inform on long-term safety and effectiveness of mexiletine in symptomatic management of myotonia in NDM adults in a real-world setting.