title: Mexiletine for symptoms and signs of myotonia in nondystrophic myotonia: a randomized controlled trial.
abstract: BACKGROUND
  Nondystrophic myotonias (NDMs) are rare diseases caused by mutations in skeletal muscle ion channels. Patients experience delayed muscle relaxation causing functionally limiting stiffness and pain. Mexiletine-induced sodium channel blockade reduced myotonia in small studies; however, as is common in rare diseases, larger studies of safety and efficacy have not previously been considered feasible.
  
  
  OBJECTIVE
  To determine the effects of mexiletine for symptoms and signs of myotonia in patients with NDMs.
  
  
  METHODS
  A randomized, double-blind, placebo-controlled 2-period crossover study at 7 neuromuscular referral centers in 4 countries of 59 patients with NDMs conducted between December 23, 2008, and March 30, 2011, as part of the National Institutes of Health-funded Rare Disease Clinical Research Network.
  
  
  METHODS
  Oral 200-mg mexiletine or placebo capsules 3 times daily for 4 weeks, followed by the opposite intervention for 4 weeks, with 1-week washout in between.
  
  
  METHODS
  Patient-reported severity score of stiffness recorded on an interactive voice response (IVR) diary (scale of 1 = minimal to 9 = worst ever experienced). Secondary end points included IVR-reported changes in pain, weakness, and tiredness; clinical myotonia assessment; quantitative measure of handgrip myotonia; and Individualized Neuromuscular Quality of Life summary quality of life score (INQOL-QOL, percentage of maximal detrimental impact).
  
  
  RESULTS
  Mexiletine significantly improved patient-reported severity score stiffness on the IVR diary. Because of a statistically significant interaction between treatment and period for this outcome, primary end point is presented by period (period 1 means were 2.53 for mexiletine and 4.21 for placebo; difference, -1.68; 95% CI, -2.66 to -0.706; P < .001; period 2 means were 1.60 for mexiletine and 5.27 for placebo; difference, -3.68; 95% CI, -3.85 to -0.139; P = .04). Mexiletine improved the INQOL-QOL score (mexiletine, 14.0 vs placebo, 16.7; difference, -2.69; 95% CI, -4.07 to -1.30; P < .001) and decreased handgrip myotonia on clinical examination (mexiletine, 0.164 seconds vs placebo, 0.494 seconds; difference, -0.330; 95% CI, -0.633 to -0.142; P < .001). The most common adverse effect was gastrointestinal (9 mexiletine and 1 placebo). Two participants experienced transient cardiac effects that did not require stopping the study (1 in each group). One serious adverse event was determined to be not study related.
  
  
  CONCLUSIONS
  In this preliminary study of patients with NDMs, the use of mexiletine compared with placebo resulted in improved patient-reported stiffness over 4 weeks of treatment, despite some concern about the maintenance of blinding.
  
  
  BACKGROUND
  clinicaltrials.gov Identifier: NCT00832000.
authors.affiliation: Department of Neurology, University of Rochester Medical Center, Rochester, New York, USA.
authors.forename: Jeffrey M
authors.initials: JM
authors.lastname: Statland
authors.forename: Brian N
authors.initials: BN
authors.lastname: Bundy
authors.forename: Yunxia
authors.initials: Y
authors.lastname: Wang
authors.forename: Dipa Raja
authors.initials: DR
authors.lastname: Rayan
authors.forename: Jaya R
authors.initials: JR
authors.lastname: Trivedi
authors.forename: Valeria A
authors.initials: VA
authors.lastname: Sansone
authors.forename: Mohammad K
authors.initials: MK
authors.lastname: Salajegheh
authors.forename: Shannon L
authors.initials: SL
authors.lastname: Venance
authors.forename: Emma
authors.initials: E
authors.lastname: Ciafaloni
authors.forename: Emma
authors.initials: E
authors.lastname: Matthews
authors.forename: Giovanni
authors.initials: G
authors.lastname: Meola
authors.forename: Laura
authors.initials: L
authors.lastname: Herbelin
authors.forename: Robert C
authors.initials: RC
authors.lastname: Griggs
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Barohn
authors.forename: Michael G
authors.initials: MG
authors.lastname: Hanna
mesh_terms: D000284:Administration, Oral; D000293:Adolescent; D000328:Adult; D000368:Aged; D000889:Anti-Arrhythmia Agents / Q000009:adverse effects / Q000627:therapeutic use*; D018592:Cross-Over Studies; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D008297:Male; D008801:Mexiletine / Q000009:adverse effects / Q000627:therapeutic use*; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000503:physiopathology; D009222:Myotonia / Q000188:drug therapy*; D010146:Pain / Q000188:drug therapy / Q000209:etiology; D011788:Quality of Life; D012720:Severity of Illness Index; D015222:Sodium Channels / Q000187:drug effects; D055815:Young Adult
chemical_list: D000889:Anti-Arrhythmia Agents; D015222:Sodium Channels; D008801:Mexiletine