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Clinical Studies

5306: Phase II Therapeutic Trial of Mexiletine in Non-Dystrophic Myotonia

Status: Not recruiting at this time


Please Note: We will make every effort to enroll all the patients we can, but we cannot make any guarantees that we will be able to enroll everyone in a particular study who wants to participate.

Nondystrophic myotonia (NDM) is a rare group of muscle disease caused by gene mutations in certain muscle cell proteins. Clinically, NDM patients experience muscle stiffness, pain and weakness. NDM patients are often disabled by their symptoms. Since NDM is a very uncommon disorder, there is not an extensive amount of knowledge about the clinical features of these patients or the best way to manage patients’ symptoms. Mexiletine, an antiarrhythmic medication, has been shown to be beneficial in case reports of patients with NDM and has been used by some neurologists to treat patients with myotonia. University of Kansas Medical Center, in cooperation with several specialized clinical research centers throughout the United States, Canada, and England, are conducting a clinical trial to determine if mexiletine is beneficial in treatment of NDM patients’ clinical symptoms.

About This Study

This is a randomized double-blind cross over study that has two treatment periods: first 4 weeks of treatment with mexiletine or placebo (placebo is a pill looks like mexiletine with no active ingredient), one week off treatment, followed with the second 4 weeks of treatment with mexiletine or placebo. The participant will be treated with mexiletine randomly either in the first treatment period or the second treatment period. Both the participant and the investigators are unaware of the assignment (double-blind). This is a total 9 week study with five study visits required during this time period. Approximately 60 participants will be enrolled at 6 centers.

The following procedures are part of this study:

  • Medical chart review
  • Blood draws
  • EKG
  • Pregnancy test (for females of childbearing potential)
  • Completion of questionnaire
  • Physical examination
  • Muscle testing
  • Nerve conduction studies
  • Electromyography (EMG)
  • Calling a telephone number to report symptoms
  • Taking study pills

Target Enrollment:

To be eligible to participate, you must:

  1. be at least 16 years of age
  2. have clinical symptoms or signs suggestive of myotonic disorders
  3. have presence of myotonic potentials on electromyography (EMG)
  4. be participating in the Non-Dystrophic Myotonia Natural History study or be a new patient with genetic confirmed NDM; or be a new patient with a first degree relative (parent, sibling, or child) with genetically confirmed NDM; or a new patient with clinical features of NDM in whom the mutation has not been localized, is DM1 and DM2 negative
  5. If patients are on either of the following medications, they must be on a stable dose for 30 days prior to enrollment. Medications are:
    • Fibrate acid derivatives,
    • Hydroxymethylglutaryl CoA reductase inhibitors

You are not eligible to participate if:

  1. you are unable or unwilling to provide informed consent.
  2. you have other neurological conditions that might affect the assessment of the study measurements.
  3. you have genetic confirmed DM1 (CTG > 50 repeats), or DM2.
  4. you have existing cardiac conduction defects, evidenced on EKG including but not limited to the following conditions: malignant arrhythmia or cardiac conduction disturbances (such as second degree AV block, third degree AV block, or prolonged QT interval >500 ms or QRS duration > 150 msec).
  5. you currently use any of the following antiarrhythmic medication for a cardiac disorder: flecainide acetate, encainide, disopyramide, procainamide, quinidine, propafenone or mexiletine.
  6. you are a women who is pregnant or lactating.
  7. you are currently on medications for myotonia such as phenytoin and flecainide acetate within 5 days of enrollment, carbamazepine and mexiletine within 3 days of enrollment, or acetazolamide, propafenone, procainamide, disopyramide, quinidine and encainide within 2 days of enrollment. 
  8. you have an existing permanent pacemaker.
  9. you have renal or hepatic disease, heart failure, or seizure disorders.
  10. you are on medications that produce myotonia. This includes one or more of the following:
    1. chloroquine
    2. colchicine

How to Participate:

In order to participate in a study, you must personally contact the study coordinator by phone or by e-mail. Please use the information below to inquire about participation.

Laura Herbelin, BS
Phone: 913-588-5095

  • London Health Sciences Center, London, Ontario, Canada
  • University of Kansas Medical Center, Kansas City, Kansas
  • University of Milan, Milan, Italy
  • University of Rochester, Rochester, New York
  • University of Texas Southwestern at Dallas, Dallas, Texas