Effectiveness of Mexiletine for Treating People With Non-Dystrophic Myotonia

Non-Dystrophic Myotonia Clinical Trial

Official title: Phase II Therapeutic Trial of Mexiletine in Non-Dystrophic Myotonia

Status Completed

Clinical Trial Summary

Nondystrophic myotonias (NDM) are neuromuscular disorders caused by genetic abnormalities in certain muscle cell membrane proteins. The proteins affect muscle contraction. Individuals with NDM experience limited muscle relaxation, which then can cause pain, weakness, incoordination, and impaired physical activity and function. Because NDM is very rare, information on the best way to treat people with the disorders is lacking, and there are no FDA-approved therapies. The purpose of this study is to determine the effectiveness of the medication mexiletine in treating people with NDM.

Clinical Trial Description

NDM are neuromuscular disorders that are caused by mutations in skeletal muscle ion channels, usually voltage-dependent sodium and chloride channels. The poorly functioning channels result in impaired muscle relaxation after contraction, which is also called myotonia. Mexiletine is an antiarrhythmic medication that has a high affinity for muscle sodium channels and may have the ability to correct delayed inactivation of sodium channels. In case reports and single-blind clinical trials, mexiletine was shown to reduce symptoms of myotonia. Currently, there is no standard strategy for treating people with NDM, and effective treatment options are needed. This study will determine the effectiveness of mexiletine in treating people with NDM.

Participation in this study will last 9 weeks and will involve two separate 4-week treatment periods, with a 1-week washout period between them. During the first treatment period, participants will be randomly assigned to receive either mexiletine or placebo, both of which will be taken three times a day. This will be followed by 1 week of no treatment. During the second treatment period, participants will receive whichever treatment they did not receive initially and will follow the same dosing schedule.

Participants will attend five study visits that will occur at screening and Weeks 0, 4, 5, and 9. Screening will include blood and urine sampling, electrocardiography (EKG), and a medical history. The remaining visits will include a physical examination, a grip test, exercise tests, nerve conduction tests, blood sampling, questionnaires, and electromyography (EMG). EKG will be repeated at Weeks 4, 5, and 9. Throughout the study, participants will phone in daily to report their symptoms. There will be no follow-up visits.

Funded by FDAOPD RO1 0003454. ;

Study Design

Allocation: Randomized, Endpoint Classification: Efficacy Study, Intervention Model: Crossover Assignment, Masking: Double Blind (Subject, Outcomes Assessor), Primary Purpose: Treatment

Related Conditions & MeSH terms

• Myotonia
• Non-Dystrophic Myotonia

• NCT number: NCT00832000
• Study type: Interventional
• Source: University of Kansas Medical Center
• Status: Completed
• Phase: Phase 2
• Start date: December 2008
• Completion date: March 2011