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Elettreby AM, Elnaga AAA, Alsaied MA, Ewis DK, Sharkawy AM, Fareed R, Alderbi GM. Effectiveness and safety of mexiletine versus placebo in patients with myotonia: a systematic review and meta-analysis. Neurol Sci 2024; 45:3989-4001. [PMID: 38403671 DOI: 10.1007/s10072-024-07412-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2023] [Accepted: 02/16/2024] [Indexed: 02/27/2024]
Abstract
BACKGROUND The rare nature of dystrophic and non-dystrophic myotonia has limited the available evidence on the efficacy of mexiletine as a potential treatment. To address this gap, we conducted a systematic review and meta-analysis to evaluate the effectiveness and safety of mexiletine for both dystrophic and non-dystrophic myotonic patients. METHODS The search was conducted on various electronic databases up to March 2023, for randomized clinical trials (RCTs) comparing mexiletine versus placebo in myotonic patients. A risk of bias assessment was carried out, and relevant data was extracted manually into an online sheet. RevMan software (version 5.4) was employed for analysis. RESULTS A total of five studies, comprising 186 patients, were included in the meta-analysis. Our findings showed that mexiletine was significantly more effective than placebo in improving stiffness score (SMD = - 1.19, 95% CI [- 1.53, - 0.85]), as well as in reducing hand grip myotonia (MD = - 1.36 s, 95% CI [- 1.83, - 0.89]). Mexiletine also significantly improved SF-36 Physical and Mental Component Score in patients with non-dystrophic myotonia only. Regarding safety, mexiletine did not significantly alter ECG parameters but was associated with greater gastrointestinal symptoms (GIT) compared to placebo (RR 3.7, 95% CI [1.79, 7.64]). Other adverse events showed no significant differences. CONCLUSION The results support that mexiletine is effective and safe in myotonic patients; however, it is associated with a higher risk of GIT symptoms. Due to the scarcity of published RCTs and the prevalence of GIT symptoms, we recommend further well-designed RCTs testing various drug combinations to reduce GIT symptoms.
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Affiliation(s)
- Abdelrahman Mohammed Elettreby
- Faculty of Medicine, Mansoura University, El Gomhouria St, Mansoura, 35511, Egypt.
- Medical Research Group of Egypt, Negida Academy LLC, Arlington, MA, 02474, USA.
| | - Ahmed Abdullah Abo Elnaga
- Faculty of Medicine, Mansoura University, El Gomhouria St, Mansoura, 35511, Egypt
- Medical Research Group of Egypt, Negida Academy LLC, Arlington, MA, 02474, USA
| | - Mohamed Ahmed Alsaied
- Faculty of Medicine, Mansoura University, El Gomhouria St, Mansoura, 35511, Egypt
- Medical Research Group of Egypt, Negida Academy LLC, Arlington, MA, 02474, USA
| | - Dalia Kamal Ewis
- Medical Research Group of Egypt, Negida Academy LLC, Arlington, MA, 02474, USA
- Faculty of Medicine, Beni Suef University, Beni Suef, Egypt
| | - Aya Mohammed Sharkawy
- Medical Research Group of Egypt, Negida Academy LLC, Arlington, MA, 02474, USA
- Faculty of Medicine, South Valley University, Qena, Egypt
| | - Rahma Fareed
- Medical Research Group of Egypt, Negida Academy LLC, Arlington, MA, 02474, USA
- Faculty of Pharmacy, Beni Suef University, Beni Suef, Egypt
| | - Gehad Magdy Alderbi
- Medical Research Group of Egypt, Negida Academy LLC, Arlington, MA, 02474, USA
- Faculty of Pharmacy, Beni Suef University, Beni Suef, Egypt
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Hakimi M, Burnham T, Ramsay J, Cheung JW, Goyal NA, Jefferies JL, Donaldson D. Electrophysiologic and Cardiovascular Manifestations of Duchenne and Becker Muscular Dystrophies. Heart Rhythm 2024:S1547-5271(24)02882-0. [PMID: 38997055 DOI: 10.1016/j.hrthm.2024.07.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/25/2024] [Revised: 07/01/2024] [Accepted: 07/03/2024] [Indexed: 07/14/2024]
Abstract
BACKGROUND There have been significant advances in the diagnosis and management of the hereditary muscular disorders Duchenne and Becker Muscular Dystrophy (DMD and BMD). Cardiac electrophysiologic and Cardiovascular involvement has long been important in the surveillance, care, and prognosis of patients with both BMD and DMD, and is the leading cause of mortality in patients with DMD. With improved long-term prognosis, rhythm disorders and progressive cardiomyopathy with resultant heart failure are increasingly common. OBJECTIVES This review aims to provide an overview to electrophysiologists and cardiologists of the cardiac electrophysiologic phenotypes and genetics of the BMD and DMD and highlight the recent discoveries that have advanced clinical course and management. METHODS A systematic review was performed in the diagnosis and management of Duchenne and Becker muscular dystrophies. The Cochrane Library, PubMed, MEDLINE, the Europe PubMed Central, AMED, and EMBASE database were accessed for available evidence. The research reported in this paper adhered to PRISMA guidelines. RESULTS Evidence from randomized control trials and studies cited in expert consensus and practice guidelines are examined. Advanced imaging techniques and a spectrum of rhythm disorders associated with the progressive cardiomyopathy are presented. Early initiation of heart failure therapies, the role of cardiac implantable devices, and novel gene therapies approved for use with the potential to alter the disease course are discussed. CONCLUSION DMD and BMD patients may have profound cardiac and cardiac electrophysiologic involvement, which when diagnosed and treated earlier, could lead to improved outcomes.
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Affiliation(s)
- Matthew Hakimi
- Weill Cornell Medical; Division of Cardiology; New York, NY
| | | | - Jay Ramsay
- Department of Medicine and Division of Cardiology
| | - Jim W Cheung
- Weill Cornell Medical; Division of Cardiology; New York, NY
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3
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Lidonnici D, Brambilla P, Ravasio R, Zozulya-Weidenfeller A, Beiderbeck A, van Aswegen M, Oliveira R, Sansone VA. Expert Insights from a Delphi-driven Neurologists' Panel: Real-world Mexiletine use in Patients with Myotonic Disorders in Italy. J Neuromuscul Dis 2024; 11:411-423. [PMID: 38306059 DOI: 10.3233/jnd-230115] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2024]
Abstract
Background Myotonic disorders, such as non-dystrophic myotonias (NDMs) and myotonic dystrophies (DMs) are characterized by a delay in muscle relaxation after a contraction stimulus. There is general consensus that protocols to treat myotonia need to be implemented. Objective Mexiletine is the only pharmacological agent approved for the symptomatic treatment of myotonia in adult patients with NDM and is considered to be the first-line treatment for DMs; however, its production in Italy was halted in 2022 making its availability to patients problematic. Methods A panel of 8 Italian neurologists took part in a two-round Delphi panel between June and October 2022, analyzing the current use of mexiletine in Italian clinical practice. Results The panelists assist 1126 patients (69% DM type1, 18% NDM and 13% DM type2). Adult NDM patients receive, on average, 400-600 mg of mexiletine hydrochloride (HCl) while adult DM patients receive 100-600 mg, per day in the long-term. The severity of symptoms is considered the main reason to start mexiletine treatment for both NDM and DM patients. Mexiletine is reckoned to have a clinical impact for both NDM and DM patients, but currently drug access is problematic. Conclusions Mexiletine treatment is recognized to have a role in the reduction of the symptomatic burden for NDM and DM patients. Patient management could be improved by facilitating access to therapy and developing new drug formulations.
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Affiliation(s)
| | | | | | | | | | | | | | - Valeria A Sansone
- The NEMO Center, Neurorehabilitation Unit, University of Milan, ASST Niguarda Hospital, Milan, Italy
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Altamura C, Saltarella I, Campanale C, Laghetti P, Desaphy JF. Drug repurposing in skeletal muscle ion channelopathies. Curr Opin Pharmacol 2023; 68:102329. [PMID: 36512979 DOI: 10.1016/j.coph.2022.102329] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2022] [Revised: 10/26/2022] [Accepted: 11/02/2022] [Indexed: 12/14/2022]
Abstract
Skeletal muscle ion channelopathies are rare genetic diseases mainly characterized by myotonia (muscle stiffness) or periodic paralysis (muscle weakness). Here, we reviewed the available therapeutic options in non-dystrophic myotonias (NDM) and periodic paralyses (PP), which consists essentially in drug repositioning to address stiffness or weakness attacks. Empirical use followed by successful randomized clinical trials eventually led to the orphan drug designation and marketing authorization granting of mexiletine for NDM and dichlorphenamide for PP. Yet, these treatments neither consider the genetic cause of the diseases nor address the individual variability in drug response. Thus, ongoing research aims at the identification of repurposed drugs alternative to mexiletine and dichlorphenamide to allow personalization of treatment. This review highlights how drug repurposing may represent an efficient strategy in rare diseases, allowing reduction of drug development time and costs in a context in which the return on investment may be particularly challenging.
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Affiliation(s)
- Concetta Altamura
- Section of Pharmacology, Department of Precision and Regenerative Medicine, School of Medicine, University of Bari Aldo Moro, Piazza Giulo Cesare, 70124, Bari, Italy
| | - Ilaria Saltarella
- Section of Pharmacology, Department of Precision and Regenerative Medicine, School of Medicine, University of Bari Aldo Moro, Piazza Giulo Cesare, 70124, Bari, Italy
| | - Carmen Campanale
- Section of Pharmacology, Department of Precision and Regenerative Medicine, School of Medicine, University of Bari Aldo Moro, Piazza Giulo Cesare, 70124, Bari, Italy
| | - Paola Laghetti
- Section of Pharmacology, Department of Precision and Regenerative Medicine, School of Medicine, University of Bari Aldo Moro, Piazza Giulo Cesare, 70124, Bari, Italy
| | - Jean-François Desaphy
- Section of Pharmacology, Department of Precision and Regenerative Medicine, School of Medicine, University of Bari Aldo Moro, Piazza Giulo Cesare, 70124, Bari, Italy.
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5
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Boreham H. Mexiletine in the Treatment of Non-dystrophic Myotonia: Interviews with Six Medical Experts. EUROPEAN MEDICAL JOURNAL 2022. [DOI: 10.33590/emj/10197860] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Evidence from randomised controlled clinical trials demonstrates that mexiletine effectively controls myotonic symptoms with a well-described safety profile. Despite this, there are still a limited number of patients on this treatment, and physicians from expert neuromuscular centres may not be fully aware of the potential benefits of mexiletine treatment, including improvements in patients’ quality of life (QoL), the impact on activities of daily living, and the favourable safety profile, even in younger patients.
During this ‘Meet the Experts’ interview series, five neurologists experienced in the management of non-dystrophic myotonias (NDM), and one specialist cardiologist offered their expert insights on the clinical data and real-world evidence supporting the use of mexiletine in NDM.
Addressing patient concerns and encouraging treatment acceptance were highlighted as key steps to optimise outcomes from mexiletine therapy. The medical experts emphasised the importance of contextualising the favourable benefit-to-risk profile of mexiletine, particularly regarding cardiac safety concerns and drug monitoring requirements. The expert cardiologist further explained that, in their experience, the cardiac safety profile of mexiletine was no different in patients with NDM when compared to healthy controls used in clinical studies when used as directed.
When considering anti-myotonia treatment in patients with NDM, medical experts stressed that decision-making should be driven by the overall degree of myotonia. Healthcare professionals (HCP), therefore, need to look beyond basic clinical assessment to understand the true impact of myotonia on patients’ everyday lives.
Overall, these interviews highlighted the critical role that HCPs can play in leveraging the clinical data and managing patient expectations to ensure maximum treatment success when recommending mexiletine to patients with NDM.
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Groh WJ, Bhakta D, Tomaselli GF, Aleong RG, Teixeira RA, Amato A, Asirvatham SJ, Cha YM, Corrado D, Duboc D, Goldberger ZD, Horie M, Hornyak JE, Jefferies JL, Kääb S, Kalman JM, Kertesz NJ, Lakdawala NK, Lambiase PD, Lubitz SA, McMillan HJ, McNally EM, Milone M, Namboodiri N, Nazarian S, Patton KK, Russo V, Sacher F, Santangeli P, Shen WK, Sobral Filho DC, Stambler BS, Stöllberger C, Wahbi K, Wehrens XHT, Weiner MM, Wheeler MT, Zeppenfeld K. 2022 HRS expert consensus statement on evaluation and management of arrhythmic risk in neuromuscular disorders. Heart Rhythm 2022; 19:e61-e120. [PMID: 35500790 DOI: 10.1016/j.hrthm.2022.04.022] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/21/2022] [Accepted: 04/21/2022] [Indexed: 11/04/2022]
Abstract
This international multidisciplinary document is intended to guide electrophysiologists, cardiologists, other clinicians, and health care professionals in caring for patients with arrhythmic complications of neuromuscular disorders (NMDs). The document presents an overview of arrhythmias in NMDs followed by detailed sections on specific disorders: Duchenne muscular dystrophy, Becker muscular dystrophy, and limb-girdle muscular dystrophy type 2; myotonic dystrophy type 1 and type 2; Emery-Dreifuss muscular dystrophy and limb-girdle muscular dystrophy type 1B; facioscapulohumeral muscular dystrophy; and mitochondrial myopathies, including Friedreich ataxia and Kearns-Sayre syndrome, with an emphasis on managing arrhythmic cardiac manifestations. End-of-life management of arrhythmias in patients with NMDs is also covered. The document sections were drafted by the writing committee members according to their area of expertise. The recommendations represent the consensus opinion of the expert writing group, graded by class of recommendation and level of evidence utilizing defined criteria. The recommendations were made available for public comment; the document underwent review by the Heart Rhythm Society Scientific and Clinical Documents Committee and external review and endorsement by the partner and collaborating societies. Changes were incorporated based on these reviews. By using a breadth of accumulated available evidence, the document is designed to provide practical and actionable clinical information and recommendations for the diagnosis and management of arrhythmias and thus improve the care of patients with NMDs.
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Affiliation(s)
- William J Groh
- Ralph H. Johnson VA Medical Center and Medical University of South Carolina, Charleston, South Carolina
| | - Deepak Bhakta
- Indiana University School of Medicine, Indianapolis, Indiana
| | | | | | | | - Anthony Amato
- Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts
| | | | | | - Domenico Corrado
- Department of Cardiac, Thoracic, and Vascular Sciences, University of Padova, Padova, Italy
| | - Denis Duboc
- Cardiology Department, Hôpital Cochin, AP-HP, Université de Paris, Paris, France
| | - Zachary D Goldberger
- University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin
| | - Minoru Horie
- Shiga University of Medical Sciences, Otsu, Japan
| | | | | | - Stefan Kääb
- Department of Medicine I, University Hospital, LMU Munich, Munich, Germany
| | - Jonathan M Kalman
- Royal Melbourne Hospital and University of Melbourne, Melbourne, Victoria, Australia
| | | | - Neal K Lakdawala
- Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts
| | - Pier D Lambiase
- Barts Heart Centre, St Bartholomew's Hospital, University College London, and St Bartholomew's Hospital London, London, United Kingdom
| | | | - Hugh J McMillan
- Montreal Children's Hospital, McGill University, Montreal, Quebec, Canada
| | | | | | - Narayanan Namboodiri
- Sree Chitra Institute for Medical Sciences and Technology, Thiruvananthapuram, India
| | | | | | | | - Frederic Sacher
- Bordeaux University Hospital, LIRYC Institute, Bordeaux, France
| | | | | | | | | | - Claudia Stöllberger
- Second Medical Department with Cardiology and Intensive Care Medicine, Klinik Landstraße, Vienna, Austria
| | - Karim Wahbi
- Cardiology Department, Hôpital Cochin, AP-HP, Université de Paris, Paris, France
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7
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Treatment and Management of Disorders of Neuromuscular Hyperexcitability and Periodic Paralysis. Neuromuscul Disord 2022. [DOI: 10.1016/b978-0-323-71317-7.00018-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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Gossios TD, Providencia R, Creta A, Segal OR, Nikolenko N, Turner C, Lopes LR, Wahbi K, Savvatis K. An overview of heart rhythm disorders and management in myotonic dystrophy type 1. Heart Rhythm 2021; 19:497-504. [PMID: 34843968 DOI: 10.1016/j.hrthm.2021.11.028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/14/2021] [Revised: 11/07/2021] [Accepted: 11/22/2021] [Indexed: 11/04/2022]
Abstract
Myotonic dystrophy type 1 (DM1) is the most common adult form of muscular dystrophy, presenting with a constellation of systemic findings secondary to a CTG triplet expansion of the noncoding region of the DMPK gene. Cardiac involvement is frequent, with conduction disease and supraventricular and ventricular arrhythmias being the most prevalent cardiac manifestations, often developing from a young age. The development of cardiac arrhythmias has been linked to increased morbidity and mortality, with sudden cardiac death well described. Strategies to mitigate risk of arrhythmic death have been developed. In this review, we outline the current knowledge on the pathophysiology of rhythm abnormalities in patients with myotonic dystrophy and summarize available knowledge on arrhythmic risk stratification. We also review management strategies from an electrophysiological perspective, attempting to underline the substantial unmet need to address residual arrhythmic risks for this population.
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Affiliation(s)
- Thomas D Gossios
- Inherited Cardiac Conditions Unit, Barts Heart Centre, St. Bartholomew's Hospital, London, United Kingdom.
| | - Rui Providencia
- Department of Cardiology, Barts Heart Centre, St. Bartholomew's Hospital, London, United Kingdom
| | - Antonio Creta
- Department of Cardiology, Barts Heart Centre, St. Bartholomew's Hospital, London, United Kingdom
| | - Oliver R Segal
- Department of Cardiology, Barts Heart Centre, St. Bartholomew's Hospital, London, United Kingdom
| | - Nikoletta Nikolenko
- National Hospital for Neurology and Neurosurgery, University College London Hospital, London, United Kingdom
| | - Chris Turner
- National Hospital for Neurology and Neurosurgery, University College London Hospital, London, United Kingdom
| | - Luis R Lopes
- Inherited Cardiac Conditions Unit, Barts Heart Centre, St. Bartholomew's Hospital, London, United Kingdom; Centre for Heart Muscle Disease, Institute of Cardiovascular Science, University College London Hospital, London, United Kingdom
| | - Karim Wahbi
- APHP, Cochin Hospital, Cardiology Department, FILNEMUS, Paris-Descartes, Sorbonne Paris Cité University, Paris, France
| | - Konstantinos Savvatis
- Inherited Cardiac Conditions Unit, Barts Heart Centre, St. Bartholomew's Hospital, London, United Kingdom
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Mousele C, Matthews E, Pitceathly RDS, Hanna MG, MacDonald S, Savvatis K, Carr A, Turner C. Long-term Safety and Efficacy of Mexiletine in Myotonic Dystrophy Types 1 and 2. Neurol Clin Pract 2021; 11:e682-e685. [PMID: 34840883 PMCID: PMC8610501 DOI: 10.1212/cpj.0000000000001073] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2020] [Accepted: 02/10/2021] [Indexed: 11/15/2022]
Abstract
BACKGROUND AND OBJECTIVE Myotonic dystrophy types 1 and 2 are progressive multisystem genetic disorders whose core clinical feature is myotonia. Mexiletine, an antagonist of voltage-gated sodium channels, is a recommended antimyotonic agent in the nondystrophic myotonias, but its use in myotonic dystrophy is limited because of lack of data regarding its long-term efficacy and safety profile. METHODS To address this issue, this study retrospectively evaluated patients with myotonic dystrophy receiving mexiletine over a mean time period of 32.9 months (range 0.1-216 months). RESULTS This study demonstrated that 96% of patients reported some improvement in myotonia symptoms with mexiletine treatment. No clinically relevant cardiac adverse events were associated with the long-term use of mexiletine. CONCLUSIONS These findings support that mexiletine is both safe and effective when used long-term in myotonic dystrophy. CLASSIFICATION OF EVIDENCE This study provides Class IV evidence that mexiletine is a well-tolerated and effective treatment for myotonic dystrophy types 1 and 2.
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Affiliation(s)
- Christina Mousele
- UCL Queen Square Institute of Neurology and The National Hospital for Neurology and Neurosurgery (CM); Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology and The National Hospital for Neurology and Neurosurgery (EM, RDSP, MGH, AC, CT); The National Hospital for Neurology and Neurosurgery (SM), Atkinson-Morley Neuromuscular Centre (EM); and Inherited Cardiovascular Diseases Unit, Barts Health Centre, Barts Healthcare NHS Trust (KS), London, United Kingdom
| | - Emma Matthews
- UCL Queen Square Institute of Neurology and The National Hospital for Neurology and Neurosurgery (CM); Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology and The National Hospital for Neurology and Neurosurgery (EM, RDSP, MGH, AC, CT); The National Hospital for Neurology and Neurosurgery (SM), Atkinson-Morley Neuromuscular Centre (EM); and Inherited Cardiovascular Diseases Unit, Barts Health Centre, Barts Healthcare NHS Trust (KS), London, United Kingdom
| | - Robert D S Pitceathly
- UCL Queen Square Institute of Neurology and The National Hospital for Neurology and Neurosurgery (CM); Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology and The National Hospital for Neurology and Neurosurgery (EM, RDSP, MGH, AC, CT); The National Hospital for Neurology and Neurosurgery (SM), Atkinson-Morley Neuromuscular Centre (EM); and Inherited Cardiovascular Diseases Unit, Barts Health Centre, Barts Healthcare NHS Trust (KS), London, United Kingdom
| | - Michael G Hanna
- UCL Queen Square Institute of Neurology and The National Hospital for Neurology and Neurosurgery (CM); Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology and The National Hospital for Neurology and Neurosurgery (EM, RDSP, MGH, AC, CT); The National Hospital for Neurology and Neurosurgery (SM), Atkinson-Morley Neuromuscular Centre (EM); and Inherited Cardiovascular Diseases Unit, Barts Health Centre, Barts Healthcare NHS Trust (KS), London, United Kingdom
| | - Susan MacDonald
- UCL Queen Square Institute of Neurology and The National Hospital for Neurology and Neurosurgery (CM); Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology and The National Hospital for Neurology and Neurosurgery (EM, RDSP, MGH, AC, CT); The National Hospital for Neurology and Neurosurgery (SM), Atkinson-Morley Neuromuscular Centre (EM); and Inherited Cardiovascular Diseases Unit, Barts Health Centre, Barts Healthcare NHS Trust (KS), London, United Kingdom
| | - Konstantinos Savvatis
- UCL Queen Square Institute of Neurology and The National Hospital for Neurology and Neurosurgery (CM); Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology and The National Hospital for Neurology and Neurosurgery (EM, RDSP, MGH, AC, CT); The National Hospital for Neurology and Neurosurgery (SM), Atkinson-Morley Neuromuscular Centre (EM); and Inherited Cardiovascular Diseases Unit, Barts Health Centre, Barts Healthcare NHS Trust (KS), London, United Kingdom
| | - Aisling Carr
- UCL Queen Square Institute of Neurology and The National Hospital for Neurology and Neurosurgery (CM); Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology and The National Hospital for Neurology and Neurosurgery (EM, RDSP, MGH, AC, CT); The National Hospital for Neurology and Neurosurgery (SM), Atkinson-Morley Neuromuscular Centre (EM); and Inherited Cardiovascular Diseases Unit, Barts Health Centre, Barts Healthcare NHS Trust (KS), London, United Kingdom
| | - Christopher Turner
- UCL Queen Square Institute of Neurology and The National Hospital for Neurology and Neurosurgery (CM); Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology and The National Hospital for Neurology and Neurosurgery (EM, RDSP, MGH, AC, CT); The National Hospital for Neurology and Neurosurgery (SM), Atkinson-Morley Neuromuscular Centre (EM); and Inherited Cardiovascular Diseases Unit, Barts Health Centre, Barts Healthcare NHS Trust (KS), London, United Kingdom
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Heatwole C, Luebbe E, Rosero S, Eichinger K, Martens W, Hilbert J, Dekdebrun J, Dilek N, Zizzi C, Johnson N, Puwanant A, Tawil R, Schifitto G, Beck CA, Richeson JF, Zareba W, Thornton C, McDermott MP, Moxley R. Mexiletine in Myotonic Dystrophy Type 1: A Randomized, Double-Blind, Placebo-Controlled Trial. Neurology 2021; 96:e228-e240. [PMID: 33046619 PMCID: PMC7905778 DOI: 10.1212/wnl.0000000000011002] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2019] [Accepted: 08/24/2020] [Indexed: 12/27/2022] Open
Abstract
OBJECTIVE To assess mexiletine's long-term safety and effect on 6-minute walk distance in a well-defined cohort of patients with myotonic dystrophy type 1 (DM1). METHODS We performed a randomized, double-blind, placebo-controlled trial of mexiletine (150 mg 3 times daily) to evaluate its efficacy and safety in a homogenous cohort of adult ambulatory patients with DM1. The primary outcome was change in 6-minute walk distance at 6 months. Secondary outcomes included changes in hand grip myotonia, strength, swallowing, forced vital capacity, lean muscle mass, Myotonic Dystrophy Health Index scores, and 24-hour Holter and ECG results at 3 and 6 months. RESULTS Forty-two participants were randomized and 40 completed the 6-month follow-up (n = 20 in both groups). No significant effects of mexiletine were observed on 6-minute walk distance, but hand grip myotonia was improved with mexiletine treatment. There were no differences between the mexiletine and placebo groups with respect to the frequency or type of adverse events. Changes in PR, QRS, and QTc intervals were similar in mexiletine- and placebo-treated participants. CONCLUSIONS There was no benefit of mexiletine on 6-minute walk distance at 6 months. Although mexiletine had a sustained positive effect on objectively measured hand grip myotonia, this was not seen in measures reflecting participants' perceptions of their myotonia. No effects of mexiletine on cardiac conduction measures were seen over the 6-month follow-up period. CLASSIFICATION OF EVIDENCE This study provides Class I evidence that for ambulatory patients with DM1, mexiletine does not significantly change 6-minute walk distance at 6 months.
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Affiliation(s)
- Chad Heatwole
- From the Department of Neurology (C.H., E.L., S.R., K.E., W.M., J.H., J.D., N.D., C.Z., R.T., G.S., C.A.B., J.F.R., W.Z., C.T., M.P.M., R.M.), University of Rochester, MN; Virginia Commonwealth University (N.J.), Richmond; and Wake Forest Baptist Health (A.P.), Winston-Salem, NC.
| | - Elizabeth Luebbe
- From the Department of Neurology (C.H., E.L., S.R., K.E., W.M., J.H., J.D., N.D., C.Z., R.T., G.S., C.A.B., J.F.R., W.Z., C.T., M.P.M., R.M.), University of Rochester, MN; Virginia Commonwealth University (N.J.), Richmond; and Wake Forest Baptist Health (A.P.), Winston-Salem, NC
| | - Spencer Rosero
- From the Department of Neurology (C.H., E.L., S.R., K.E., W.M., J.H., J.D., N.D., C.Z., R.T., G.S., C.A.B., J.F.R., W.Z., C.T., M.P.M., R.M.), University of Rochester, MN; Virginia Commonwealth University (N.J.), Richmond; and Wake Forest Baptist Health (A.P.), Winston-Salem, NC
| | - Katy Eichinger
- From the Department of Neurology (C.H., E.L., S.R., K.E., W.M., J.H., J.D., N.D., C.Z., R.T., G.S., C.A.B., J.F.R., W.Z., C.T., M.P.M., R.M.), University of Rochester, MN; Virginia Commonwealth University (N.J.), Richmond; and Wake Forest Baptist Health (A.P.), Winston-Salem, NC
| | - William Martens
- From the Department of Neurology (C.H., E.L., S.R., K.E., W.M., J.H., J.D., N.D., C.Z., R.T., G.S., C.A.B., J.F.R., W.Z., C.T., M.P.M., R.M.), University of Rochester, MN; Virginia Commonwealth University (N.J.), Richmond; and Wake Forest Baptist Health (A.P.), Winston-Salem, NC
| | - James Hilbert
- From the Department of Neurology (C.H., E.L., S.R., K.E., W.M., J.H., J.D., N.D., C.Z., R.T., G.S., C.A.B., J.F.R., W.Z., C.T., M.P.M., R.M.), University of Rochester, MN; Virginia Commonwealth University (N.J.), Richmond; and Wake Forest Baptist Health (A.P.), Winston-Salem, NC
| | - Jeanne Dekdebrun
- From the Department of Neurology (C.H., E.L., S.R., K.E., W.M., J.H., J.D., N.D., C.Z., R.T., G.S., C.A.B., J.F.R., W.Z., C.T., M.P.M., R.M.), University of Rochester, MN; Virginia Commonwealth University (N.J.), Richmond; and Wake Forest Baptist Health (A.P.), Winston-Salem, NC
| | - Nuran Dilek
- From the Department of Neurology (C.H., E.L., S.R., K.E., W.M., J.H., J.D., N.D., C.Z., R.T., G.S., C.A.B., J.F.R., W.Z., C.T., M.P.M., R.M.), University of Rochester, MN; Virginia Commonwealth University (N.J.), Richmond; and Wake Forest Baptist Health (A.P.), Winston-Salem, NC
| | - Christine Zizzi
- From the Department of Neurology (C.H., E.L., S.R., K.E., W.M., J.H., J.D., N.D., C.Z., R.T., G.S., C.A.B., J.F.R., W.Z., C.T., M.P.M., R.M.), University of Rochester, MN; Virginia Commonwealth University (N.J.), Richmond; and Wake Forest Baptist Health (A.P.), Winston-Salem, NC
| | - Nicholas Johnson
- From the Department of Neurology (C.H., E.L., S.R., K.E., W.M., J.H., J.D., N.D., C.Z., R.T., G.S., C.A.B., J.F.R., W.Z., C.T., M.P.M., R.M.), University of Rochester, MN; Virginia Commonwealth University (N.J.), Richmond; and Wake Forest Baptist Health (A.P.), Winston-Salem, NC
| | - Araya Puwanant
- From the Department of Neurology (C.H., E.L., S.R., K.E., W.M., J.H., J.D., N.D., C.Z., R.T., G.S., C.A.B., J.F.R., W.Z., C.T., M.P.M., R.M.), University of Rochester, MN; Virginia Commonwealth University (N.J.), Richmond; and Wake Forest Baptist Health (A.P.), Winston-Salem, NC
| | - Rabi Tawil
- From the Department of Neurology (C.H., E.L., S.R., K.E., W.M., J.H., J.D., N.D., C.Z., R.T., G.S., C.A.B., J.F.R., W.Z., C.T., M.P.M., R.M.), University of Rochester, MN; Virginia Commonwealth University (N.J.), Richmond; and Wake Forest Baptist Health (A.P.), Winston-Salem, NC
| | - Giovanni Schifitto
- From the Department of Neurology (C.H., E.L., S.R., K.E., W.M., J.H., J.D., N.D., C.Z., R.T., G.S., C.A.B., J.F.R., W.Z., C.T., M.P.M., R.M.), University of Rochester, MN; Virginia Commonwealth University (N.J.), Richmond; and Wake Forest Baptist Health (A.P.), Winston-Salem, NC
| | - Christopher A Beck
- From the Department of Neurology (C.H., E.L., S.R., K.E., W.M., J.H., J.D., N.D., C.Z., R.T., G.S., C.A.B., J.F.R., W.Z., C.T., M.P.M., R.M.), University of Rochester, MN; Virginia Commonwealth University (N.J.), Richmond; and Wake Forest Baptist Health (A.P.), Winston-Salem, NC
| | - J Franklin Richeson
- From the Department of Neurology (C.H., E.L., S.R., K.E., W.M., J.H., J.D., N.D., C.Z., R.T., G.S., C.A.B., J.F.R., W.Z., C.T., M.P.M., R.M.), University of Rochester, MN; Virginia Commonwealth University (N.J.), Richmond; and Wake Forest Baptist Health (A.P.), Winston-Salem, NC
| | - Wojciech Zareba
- From the Department of Neurology (C.H., E.L., S.R., K.E., W.M., J.H., J.D., N.D., C.Z., R.T., G.S., C.A.B., J.F.R., W.Z., C.T., M.P.M., R.M.), University of Rochester, MN; Virginia Commonwealth University (N.J.), Richmond; and Wake Forest Baptist Health (A.P.), Winston-Salem, NC
| | - Charles Thornton
- From the Department of Neurology (C.H., E.L., S.R., K.E., W.M., J.H., J.D., N.D., C.Z., R.T., G.S., C.A.B., J.F.R., W.Z., C.T., M.P.M., R.M.), University of Rochester, MN; Virginia Commonwealth University (N.J.), Richmond; and Wake Forest Baptist Health (A.P.), Winston-Salem, NC
| | - Michael P McDermott
- From the Department of Neurology (C.H., E.L., S.R., K.E., W.M., J.H., J.D., N.D., C.Z., R.T., G.S., C.A.B., J.F.R., W.Z., C.T., M.P.M., R.M.), University of Rochester, MN; Virginia Commonwealth University (N.J.), Richmond; and Wake Forest Baptist Health (A.P.), Winston-Salem, NC
| | - Richard Moxley
- From the Department of Neurology (C.H., E.L., S.R., K.E., W.M., J.H., J.D., N.D., C.Z., R.T., G.S., C.A.B., J.F.R., W.Z., C.T., M.P.M., R.M.), University of Rochester, MN; Virginia Commonwealth University (N.J.), Richmond; and Wake Forest Baptist Health (A.P.), Winston-Salem, NC
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11
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Vio R, Zorzi A, Bello L, Bozzoni V, Botta A, Rivezzi F, Leoni L, Migliore F, Bertaglia E, Iliceto S, Pegoraro E, Corrado D, Calore C. Evaluation of mexiletine effect on conduction delay and bradyarrhythmic complications in patients with myotonic dystrophy type 1 over long-term follow-up. Heart Rhythm 2020; 17:1944-1950. [DOI: 10.1016/j.hrthm.2020.05.043] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/10/2020] [Revised: 05/19/2020] [Accepted: 05/20/2020] [Indexed: 01/15/2023]
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12
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Stunnenberg BC, LoRusso S, Arnold WD, Barohn RJ, Cannon SC, Fontaine B, Griggs RC, Hanna MG, Matthews E, Meola G, Sansone VA, Trivedi JR, van Engelen BG, Vicart S, Statland JM. Guidelines on clinical presentation and management of nondystrophic myotonias. Muscle Nerve 2020; 62:430-444. [PMID: 32270509 PMCID: PMC8117169 DOI: 10.1002/mus.26887] [Citation(s) in RCA: 46] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2020] [Revised: 04/01/2020] [Accepted: 04/04/2020] [Indexed: 12/26/2022]
Abstract
The nondystrophic myotonias are rare muscle hyperexcitability disorders caused by gain-of-function mutations in the SCN4A gene or loss-of-function mutations in the CLCN1 gene. Clinically, they are characterized by myotonia, defined as delayed muscle relaxation after voluntary contraction, which leads to symptoms of muscle stiffness, pain, fatigue, and weakness. Diagnosis is based on history and examination findings, the presence of electrical myotonia on electromyography, and genetic confirmation. In the absence of genetic confirmation, the diagnosis is supported by detailed electrophysiological testing, exclusion of other related disorders, and analysis of a variant of uncertain significance if present. Symptomatic treatment with a sodium channel blocker, such as mexiletine, is usually the first step in management, as well as educating patients about potential anesthetic complications.
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Affiliation(s)
- Bas C. Stunnenberg
- Department of Neurology, Radboud University Medical Center, Nijmegen, the Netherlands
| | - Samantha LoRusso
- Department of Neurology, Ohio State University Wexner Medical Center, Columbus, Ohio
| | - W. David Arnold
- Department of Neurology, Ohio State University Wexner Medical Center, Columbus, Ohio
| | - Richard J. Barohn
- Department of Neurology, University of Kansas Medical Center, Kansas City, Kansas
| | - Stephen C. Cannon
- Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California
| | - Bertrand Fontaine
- Assistance Publique-Hôpitaix de Paris, Sorbonne Université, INSERM, Service of Neuro-Myology and UMR 974, Institute of Myology, University Hospital Pitié-Salpêtrière, Paris, France
| | - Robert C. Griggs
- Department of Neurology, University of Rochester, Rochester, New York
| | - Michael G. Hanna
- MRC Centre for Neuromuscular Diseases, Department of Neuromuscular diseases, UCL Queen Square Institute of Neurology, United Kingdom
| | - Emma Matthews
- MRC Centre for Neuromuscular Diseases, Department of Neuromuscular diseases, UCL Queen Square Institute of Neurology, United Kingdom
| | - Giovanni Meola
- Department of Neurorehabilitation Sciences, Casa Cura Policlinico, Milan, Italy
- Department of Biomedical Sciences for Health, University of Milan, Milan, Italy
| | - Valeria A. Sansone
- Department of Biomedical Sciences for Health, University of Milan, Milan, Italy
- Neurorehabilitation Unit, University of Milan, NEuroMuscular Omnicentre (NEMO), Fondazione Serena Onlus, Milan, Italy
| | - Jaya R. Trivedi
- Department of Neurology and Neurotherapeutics, UT Southwestern Medical Center, Dallas, Texas
| | | | - Savine Vicart
- Assistance Publique-Hôpitaix de Paris, Sorbonne Université, INSERM, Service of Neuro-Myology and UMR 974, Institute of Myology, University Hospital Pitié-Salpêtrière, Paris, France
| | - Jeffrey M. Statland
- Department of Neurology, University of Kansas Medical Center, Kansas City, Kansas
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Abstract
PURPOSE OF REVIEW This article aims to review the current and upcoming treatment options of primary muscle channelopathies including the non-dystrophic myotonias and periodic paralyses. RECENT FINDINGS The efficacy of mexiletine in the treatment of myotonia is now supported by two randomised placebo-controlled trials, one of which utilised a novel aggregated n-of-1 design. This has resulted in licencing of the drug via orphan drug status. There is also good evidence that mexiletine is well tolerated and safe in this patient group without the need for intensive monitoring. A range of alternative antimyotonic treatment options include lamotrigine, carbamazepine and ranolazine exist with variable evidence base. In vitro studies have shown insight into reasons for treatment failure of some medications with certain genotypes opening the era of mutation-specific therapy such as use of flecainide. In the periodic paralyses, the ability of MRI to distinguish between reversible oedema and irreversible fatty replacement makes it an increasingly useful tool to guide and assess pharmacological treatment. Unfortunately, the striking efficacy of bumetanide in hypokalaemic periodic paralysis animal models was not replicated in a recent pilot study in humans. SUMMARY The treatment of skeletal muscle channelopathies combines dietary and lifestyle advice together with pharmacological interventions. The rarity of these conditions remains a barrier for clinical studies but the example of the aggregated n-of-1 trial of mexiletine shows that innovative trial design can overcome these hurdles. Further research is required to test efficacy of drugs shown to have promising characteristics in preclinical experiments such as safinamide, riluzule and magnesium for myotonia or bumetanide for hypokalaemic periodic paralysis.
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Affiliation(s)
- Nantaporn Jitpimolmard
- Queen Square Centre for Neuromuscular Diseases, UCL Queen Square Institute of Neurology, UCL, London, UK
- Rehabilitation Medicine Department, Faculty of Medicine, Khon Kaen University, Khon Kaen, Thailand
| | - Emma Matthews
- Queen Square Centre for Neuromuscular Diseases, UCL Queen Square Institute of Neurology, UCL, London, UK
- Atkinson-Morley Neuromuscular Centre, St George’s University Hospitals Foundation Trust, London, UK
| | - Doreen Fialho
- Queen Square Centre for Neuromuscular Diseases, UCL Queen Square Institute of Neurology, UCL, London, UK
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14
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Suetterlin KJ, Raja Rayan D, Matthews E, Hanna MG. Mexiletine (NaMuscla) for the treatment of myotonia in non-dystrophic myotonic disorders. Expert Opin Orphan Drugs 2020. [DOI: 10.1080/21678707.2020.1739519] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Affiliation(s)
- Karen J. Suetterlin
- MRC Centre for Neuromuscular Diseases, UCL Queen Square Institute of Neurology, London, UK
| | - Dipa Raja Rayan
- MRC Centre for Neuromuscular Diseases, UCL Queen Square Institute of Neurology, London, UK
| | - Emma Matthews
- MRC Centre for Neuromuscular Diseases, UCL Queen Square Institute of Neurology, London, UK
| | - Michael G Hanna
- MRC Centre for Neuromuscular Diseases, UCL Queen Square Institute of Neurology, London, UK
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15
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Proarrhythmic Manifestations of Neuromuscular Dystrophinopathies. Cardiol Rev 2020; 29:68-72. [PMID: 32068541 DOI: 10.1097/crd.0000000000000305] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Muscular dystrophy has been an elusive term ever since it was first described in the 19th century. Introduced in 1891 by Wilhelm Heinrich Erb, muscular dystrophy has been classified as part of a larger group of genetically determined, progressive degenerative neuromuscular disorders termed "dystrophinopathies." Cardiac arrhythmias may occur during the neurologic course of the disease. Although descriptions of the dystrophinopathies have been reported in the literature, few articles address the use of antiarrhythmic pharmacotherapy in patients with muscular dystrophy. We discuss the pathophysiology of the most common dystrophinopathies, their proarrhythmic sequelae, and the therapeutic use of antiarrhythmic agents in the clinical setting.
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Clout AE, Della Pasqua O, Hanna MG, Orlu M, Pitceathly RDS. Drug repurposing in neurological diseases: an integrated approach to reduce trial and error. J Neurol Neurosurg Psychiatry 2019; 90:1270-1275. [PMID: 31171583 DOI: 10.1136/jnnp-2019-320879] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/26/2019] [Revised: 05/02/2019] [Accepted: 05/03/2019] [Indexed: 12/13/2022]
Abstract
Identifying effective disease-modifying therapies for neurological diseases remains an important challenge in drug discovery and development. Drug repurposing attempts to determine new indications for pre-existing compounds and represents a major opportunity to address this clinically unmet need. It is potentially more cost-effective and time-efficient than de novo drug development and has yielded notable successes in neurological disorders. However, across all medical disciplines, only 30% of repurposed drugs, and 10% of novel candidate molecules, gain market approval. One potentially significant contributor towards this limited success rate is an incomplete knowledge of the exposure-response relationships for the compounds of interest, and how these relate to the new indication, prior to commencing a new trial. We provide an overview of the current approach to early-stage drug repurposing and consider the issues contributing to inconclusive, or possibly falsely negative, Phase II and III trial outcomes in neurological diseases by highlighting examples that illustrate the limitations of empirical evidence generation without a strong scientific basis for the dose rationale. We conclude with a framework suggesting a translational, iterative approach, that integrates pharmacological, pharmaceutical and clinical expertise, towards preclinical and early clinical drug development. This ensures appropriate dosing regimen, route of administration and/or formulation are selected for the new indication before their evaluation in prospective clinical trials.
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Affiliation(s)
| | - Oscar Della Pasqua
- Clinical Pharmacology and Therapeutics Group, UCL School of Pharmacy, London, UK.,Clinical Pharmacology Modelling and Simulation, GlaxoSmithKline, Uxbridge, UK
| | - Michael G Hanna
- MRC Centre for Neuromuscular Diseases, UCL Queen Square Institute of Neurology and National Hospital for Neurology and Neurosurgery, London, UK.,Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, London, UK
| | - Mine Orlu
- Department of Pharmaceutics, UCL School of Pharmacy, London, UK
| | - Robert D S Pitceathly
- MRC Centre for Neuromuscular Diseases, UCL Queen Square Institute of Neurology and National Hospital for Neurology and Neurosurgery, London, UK .,Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, London, UK
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17
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Lorusso S, Kline D, Bartlett A, Freimer M, Agriesti J, Hawash AA, Rich MM, Kissel JT, David Arnold W. Open-label trial of ranolazine for the treatment of paramyotonia congenita. Muscle Nerve 2018; 59:240-243. [PMID: 30390395 DOI: 10.1002/mus.26372] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2018] [Revised: 10/27/2018] [Accepted: 10/30/2018] [Indexed: 01/16/2023]
Abstract
INTRODUCTION Paramyotonia congenita (PMC) is a nondystrophic myotonic disorder that is believed to be caused by a defect in Nav 1.4 sodium channel inactivation. Ranolazine, which acts by enhancing slow inactivation of sodium channels, has been proposed as a therapeutic option, but in vivo studies are lacking. METHODS We conducted an open-label, single-center trial of ranolazine to evaluate efficacy and tolerability in patients with PMC. Subjective symptoms of stiffness, weakness, and pain as well as clinical and electrical myotonia were evaluated. Baseline measures were compared with those after 4 weeks of treatment with ranolazine. RESULTS Ranolazine was tolerated well without any serious adverse events. Both subjective symptoms and clinical myotonia were significantly improved. Duration of myotonia was reduced according to electromyography, but this change was not statistically significant in all tested muscles. DISCUSSION Our findings support the use of ranolazine as a treatment for myotonia in PMC and suggest that a randomized, placebo-controlled trial is warranted. Muscle Nerve 59:240-243, 2019.
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Affiliation(s)
- Samantha Lorusso
- Division of Neuromuscular Disorders, Department of Neurology, The Ohio State University Wexner Medical Center, 395 West 12th Avenue, Columbus, Ohio, 43210, USA
| | - David Kline
- Center for Biostatistics, Department of Biomedical Informatics, The Ohio State University, Columbus, Ohio, USA
| | - Amy Bartlett
- Division of Neuromuscular Disorders, Department of Neurology, The Ohio State University Wexner Medical Center, 395 West 12th Avenue, Columbus, Ohio, 43210, USA
| | - Miriam Freimer
- Division of Neuromuscular Disorders, Department of Neurology, The Ohio State University Wexner Medical Center, 395 West 12th Avenue, Columbus, Ohio, 43210, USA
| | - Julie Agriesti
- Division of Neuromuscular Disorders, Department of Neurology, The Ohio State University Wexner Medical Center, 395 West 12th Avenue, Columbus, Ohio, 43210, USA
| | - Ahmed A Hawash
- Department of Neuroscience, Cell Biology and Physiology, Wright State University, Dayton, Ohio, USA
| | - Mark M Rich
- Department of Neuroscience, Cell Biology and Physiology, Wright State University, Dayton, Ohio, USA
| | - John T Kissel
- Division of Neuromuscular Disorders, Department of Neurology, The Ohio State University Wexner Medical Center, 395 West 12th Avenue, Columbus, Ohio, 43210, USA
| | - W David Arnold
- Division of Neuromuscular Disorders, Department of Neurology, The Ohio State University Wexner Medical Center, 395 West 12th Avenue, Columbus, Ohio, 43210, USA
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18
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Abstract
Skeletal muscle channelopathies are rare heterogeneous diseases with marked genotypic and phenotypic variability. These disorders cause lifetime disability and impact quality of life. Despite advances in understanding of the molecular pathology of these disorders, the diverse phenotypic manifestations remain a challenge in diagnosis, therapeutic, genetic counseling, and research planning. Electrodiagnostic testing is useful in directing the diagnosis, but has several limitations: patient discomfort, time consuming, and significant overlap of findings in muscle channelopathies. Although genetic testing is the gold standard in making a definitive diagnosis, a mutation might not be identified in many patients with a well-supported clinical diagnosis of periodic paralysis. In the recent past, there have been landmark clinical trials in non-dystrophic myotonia and periodic paralysis which are encouraging as they demonstrate the ability of robust clinical research consortia to conduct well-controlled trials of rare diseases.
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Affiliation(s)
- Lauren Phillips
- Department of Neurology and Neurotherapeutics, UT Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, Texas, 75390, USA
| | - Jaya R Trivedi
- Department of Neurology and Neurotherapeutics, UT Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, Texas, 75390, USA.
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Marakhonov AV, Varenikov GG, Skoblov MY. Sodium Channelopathies: From Molecular Physiology towards Medical Genetics. RUSS J GENET+ 2018. [DOI: 10.1134/s102279541801009x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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20
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Andersen G, Hedermann G, Witting N, Duno M, Andersen H, Vissing J. The antimyotonic effect of lamotrigine in non-dystrophic myotonias: a double-blind randomized study. Brain 2017; 140:2295-2305. [PMID: 29050397 DOI: 10.1093/brain/awx192] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2017] [Accepted: 06/17/2017] [Indexed: 11/14/2022] Open
Abstract
Mexiletine is the only drug with proven effect for treatment of non-dystrophic myotonia, but mexiletine is expensive, has limited availability and several side effects. There is therefore a need to identify other pharmacological compounds that can alleviate myotonia in non-dystrophic myotonias. Like mexiletine, lamotrigine is a sodium channel blocker, but unlike mexiletine, lamotrigine is available, inexpensive, and well tolerated. We investigated the potential of using lamotrigine for treatment of myotonia in patients with non-dystrophic myotonias. In this, randomized double-blind, placebo-controlled, two-period cross-over study, we included adult outpatients recruited from all of Denmark with clinical myotonia and genetically confirmed myotonia congenita and paramyotonia congenita for investigation at the Copenhagen Neuromuscular Center. A pharmacy produced the medication and placebo, and randomized patients in blocks of 10. Participants and investigators were all blinded to treatment until the end of the trial. In two 8-week periods, oral lamotrigine or placebo capsules were provided once daily, with increasing doses (from 25 mg, 50 mg, 150 mg to 300 mg) every second week. The primary outcome was a severity score of myotonia, the Myotonic Behaviour Scale ranging from asymptomatic (score 1) to invalidating myotonia (score 6), reported by the participants during Weeks 0 and 8 in each treatment period. Clinical myotonia was also measured and side effects were monitored. The study was registered at ClinicalTrials.gov (NCT02159963) and EudraCT (2013-003309-24). We included 26 patients (10 females, 16 males, age: 19-74 years) from 13 November 2013 to 6 July 2015. Twenty-two completed the entire study. One patient withdrew due to an allergic reaction to lamotrigine. Three patients withdrew for reasons not related to the trial intervention. The Myotonic Behaviour Scale at baseline was 3.2 ± 1.1, which changed after treatment with lamotrigine by 1.3 ± 0.2 scores (P < 0.001), but not with placebo (0.2 ± 0.1 scores, P = 0.4). The estimated effect size was 1.0 ± 0.2 (95% confidence interval = 0.5-1.5, P < 0.001, n = 22). The standardized effect size of lamotrigine was 1.5 (confidence interval: 1.2-1.8). Number needed to treat was 2.6 (P = 0.006, n = 26). No adverse or unsuspected event occurred. Common side effects occurred in both treatment groups; number needed to harm was 5.2 (P = 0.11, n = 26). Lamotrigine effectively reduced myotonia, emphasized by consistency between effects on patient-related outcomes and objective outcomes. The frequency of side effects was acceptable. Considering this and the high availability and low cost of the drug, we suggest that lamotrigine should be used as the first line of treatment for myotonia in treatment-naive patients with non-dystrophic myotonias.
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Affiliation(s)
- Grete Andersen
- Department of Neurology, Copenhagen Neuromuscular Center, University of Copenhagen, Denmark
| | - Gitte Hedermann
- Department of Neurology, Copenhagen Neuromuscular Center, University of Copenhagen, Denmark
| | - Nanna Witting
- Department of Neurology, Copenhagen Neuromuscular Center, University of Copenhagen, Denmark
| | - Morten Duno
- Department of Molecular Genetics, University of Copenhagen, Denmark
| | | | - John Vissing
- Department of Neurology, Copenhagen Neuromuscular Center, University of Copenhagen, Denmark
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21
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Arnold WD, Kline D, Sanderson A, Hawash AA, Bartlett A, Novak KR, Rich MM, Kissel JT. Open-label trial of ranolazine for the treatment of myotonia congenita. Neurology 2017; 89:710-713. [PMID: 28710329 DOI: 10.1212/wnl.0000000000004229] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2016] [Accepted: 05/18/2017] [Indexed: 01/18/2023] Open
Abstract
OBJECTIVE To determine open-label, pilot study whether ranolazine could improve signs and symptoms of myotonia and muscle stiffness in patients with myotonia congenita (MC). METHODS Thirteen participants were assessed at baseline and 2, 4, and 5 weeks. Ranolazine was started after baseline assessment (500 mg twice daily), increased as tolerated after week 2 (1,000 mg twice daily), and maintained until week 4. Outcomes included change from baseline to week 4 in self-reported severity of symptoms (stiffness, weakness, and pain), Timed Up and Go (TUG), hand grip and eyelid myotonia, and myotonia on EMG. RESULTS Self-reported severity of stiffness (p < 0.0001) and weakness (p < 0.01) was significantly improved compared with baseline. TUG and grip myotonia times were reduced (p = 0.03, p = 0.01). EMG of the abductor digiti minimi and tibialis anterior showed significantly reduced myotonia duration (p < 0.001, p < 0.01) at week 4. No participant discontinued ranolazine because of side effects. CONCLUSIONS Ranolazine appeared to be well tolerated over a period of 4 weeks in individuals with MC, and ranolazine resulted in improvement of signs and symptoms of muscle stiffness. The findings of this study suggest that ranolazine should be investigated in a larger controlled study. CLASSIFICATION OF EVIDENCE This study provides Class IV evidence that ranolazine improves myotonia in myotonia congenita.
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Affiliation(s)
- W David Arnold
- From the Department of Neurology (W.D.A., A.S., A.B., J.T.K.), The Ohio State University Wexner Medical Center; Center for Biostatistics (D.K.), Department of Biomedical Informatics, The Ohio State University, Columbus; and Neuroscience, Cell Biology, and Physiology and Neurology (A.A.H., K.R.N., M.M.R.), Wright State University, Dayton, OH.
| | - David Kline
- From the Department of Neurology (W.D.A., A.S., A.B., J.T.K.), The Ohio State University Wexner Medical Center; Center for Biostatistics (D.K.), Department of Biomedical Informatics, The Ohio State University, Columbus; and Neuroscience, Cell Biology, and Physiology and Neurology (A.A.H., K.R.N., M.M.R.), Wright State University, Dayton, OH
| | - Alan Sanderson
- From the Department of Neurology (W.D.A., A.S., A.B., J.T.K.), The Ohio State University Wexner Medical Center; Center for Biostatistics (D.K.), Department of Biomedical Informatics, The Ohio State University, Columbus; and Neuroscience, Cell Biology, and Physiology and Neurology (A.A.H., K.R.N., M.M.R.), Wright State University, Dayton, OH
| | - Ahmed A Hawash
- From the Department of Neurology (W.D.A., A.S., A.B., J.T.K.), The Ohio State University Wexner Medical Center; Center for Biostatistics (D.K.), Department of Biomedical Informatics, The Ohio State University, Columbus; and Neuroscience, Cell Biology, and Physiology and Neurology (A.A.H., K.R.N., M.M.R.), Wright State University, Dayton, OH
| | - Amy Bartlett
- From the Department of Neurology (W.D.A., A.S., A.B., J.T.K.), The Ohio State University Wexner Medical Center; Center for Biostatistics (D.K.), Department of Biomedical Informatics, The Ohio State University, Columbus; and Neuroscience, Cell Biology, and Physiology and Neurology (A.A.H., K.R.N., M.M.R.), Wright State University, Dayton, OH
| | - Kevin R Novak
- From the Department of Neurology (W.D.A., A.S., A.B., J.T.K.), The Ohio State University Wexner Medical Center; Center for Biostatistics (D.K.), Department of Biomedical Informatics, The Ohio State University, Columbus; and Neuroscience, Cell Biology, and Physiology and Neurology (A.A.H., K.R.N., M.M.R.), Wright State University, Dayton, OH
| | - Mark M Rich
- From the Department of Neurology (W.D.A., A.S., A.B., J.T.K.), The Ohio State University Wexner Medical Center; Center for Biostatistics (D.K.), Department of Biomedical Informatics, The Ohio State University, Columbus; and Neuroscience, Cell Biology, and Physiology and Neurology (A.A.H., K.R.N., M.M.R.), Wright State University, Dayton, OH
| | - John T Kissel
- From the Department of Neurology (W.D.A., A.S., A.B., J.T.K.), The Ohio State University Wexner Medical Center; Center for Biostatistics (D.K.), Department of Biomedical Informatics, The Ohio State University, Columbus; and Neuroscience, Cell Biology, and Physiology and Neurology (A.A.H., K.R.N., M.M.R.), Wright State University, Dayton, OH
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Skov M, de Paoli FV, Nielsen OB, Pedersen TH. The anti-convulsants lacosamide, lamotrigine, and rufinamide reduce myotonia in isolated human and rat skeletal muscle. Muscle Nerve 2017; 56:136-142. [PMID: 27783415 DOI: 10.1002/mus.25452] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2015] [Revised: 10/14/2016] [Accepted: 10/19/2016] [Indexed: 11/11/2022]
Abstract
INTRODUCTION In myotonia congenita, loss of ClC-1 Cl- channel function results in skeletal muscle hyperexcitability and myotonia. Anti-myotonic treatment has typically targeted the voltage-gated sodium channel in skeletal muscle (Nav1.4). In this study we explored whether 3 sodium channel-modulating anti-epileptics can reduce myotonia in isolated rat and human muscle. METHODS Dissected muscles were rendered myotonic by ClC-1 channel inhibition. The ability of the drugs to suppress myotonia was then assessed from subclinical to maximal clinical concentrations. Drug synergy was determined using isobole plots. RESULTS All drugs were capable of abolishing myotonia in both rat and human muscles. Lamotrigine and rufinamide completely suppressed myotonia at submaximal clinical concentrations, whereas lacosamide had to be raised above the maximal clinical concentration to suppress myotonia completely. A synergistic effect of lamotrigine and rufinamide was observed. CONCLUSION These findings suggest that lamotrigine and rufinamide could be considered for anti-myotonic treatment in myotonia congenita. Muscle Nerve 56: 136-142, 2017.
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Affiliation(s)
- Martin Skov
- Department of Biomedicine, Aarhus University, Ole Worms Allé 4, 8000, Aarhus C, Denmark
| | - Frank V de Paoli
- Department of Biomedicine, Aarhus University, Ole Worms Allé 4, 8000, Aarhus C, Denmark.,Department of Cardiothoracic and Vascular Surgery, Aarhus University Hospital Skejby, Aarhus, Denmark
| | - Ole B Nielsen
- Department of Biomedicine, Aarhus University, Ole Worms Allé 4, 8000, Aarhus C, Denmark
| | - Thomas H Pedersen
- Department of Biomedicine, Aarhus University, Ole Worms Allé 4, 8000, Aarhus C, Denmark
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Noto YI, Shibuya K, Vucic S, Kiernan MC. Novel therapies in development that inhibit motor neuron hyperexcitability in amyotrophic lateral sclerosis. Expert Rev Neurother 2016; 16:1147-54. [DOI: 10.1080/14737175.2016.1197774] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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Bucchia M, Ramirez A, Parente V, Simone C, Nizzardo M, Magri F, Dametti S, Corti S. Therapeutic Development in Amyotrophic Lateral Sclerosis. Clin Ther 2015; 37:668-80. [DOI: 10.1016/j.clinthera.2014.12.020] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2014] [Revised: 09/18/2014] [Accepted: 12/29/2014] [Indexed: 12/12/2022]
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Abstract
OPINION STATEMENT Neuromuscular channelopathies are heterogeneous disorders with marked phenotypic and genotypic variability. These include non-dystrophic myotonia (NDM), periodic paralysis (PP), and congenital myasthenic syndrome (CMS). Their diverse clinical manifestations remain a challenge in diagnosis and management to this date. These disorders impact quality of life and cause lifelong disabling symptoms. Treatment options are few and not FDA-approved. This is largely due to a paucity of large, randomized clinical trials in these rare diseases. Challenges of conducting such trials include the rarity of these disorders and the genetic heterogeneity. Physicians rely on off-label use of drugs to treat muscle channelopathies to reduce morbidity and improve quality of life. Besides pharmacological treatment, dietary modifications, lifestyle changes, awareness of triggers, and genetic counseling also play an important role in long-term disease management. This article reviews the current management strategies for neuromuscular channelopathies.
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Meola G, Cardani R. Myotonic dystrophies: An update on clinical aspects, genetic, pathology, and molecular pathomechanisms. Biochim Biophys Acta Mol Basis Dis 2014; 1852:594-606. [PMID: 24882752 DOI: 10.1016/j.bbadis.2014.05.019] [Citation(s) in RCA: 213] [Impact Index Per Article: 21.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2014] [Revised: 05/19/2014] [Accepted: 05/20/2014] [Indexed: 01/18/2023]
Abstract
Myotonic dystrophy (DM) is the most common adult muscular dystrophy, characterized by autosomal dominant progressive myopathy, myotonia and multiorgan involvement. To date two distinct forms caused by similar mutations have been identified. Myotonic dystrophy type 1 (DM1, Steinert's disease) is caused by a (CTG)n expansion in DMPK, while myotonic dystrophy type 2 (DM2) is caused by a (CCTG)n expansion in ZNF9/CNBP. When transcribed into CUG/CCUG-containing RNA, mutant transcripts aggregate as nuclear foci that sequester RNA-binding proteins, resulting in spliceopathy of downstream effector genes. However, it is now clear that additional pathogenic mechanism like changes in gene expression, protein translation and micro-RNA metabolism may also contribute to disease pathology. Despite clinical and genetic similarities, DM1 and DM2 are distinct disorders requiring different diagnostic and management strategies. This review is an update on the recent advances in the understanding of the molecular mechanisms behind myotonic dystrophies. This article is part of a Special Issue entitled: Neuromuscular Diseases: Pathology and Molecular Pathogenesis.
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Affiliation(s)
- Giovanni Meola
- Department of Neurology, IRCCS Policlinico San Donato, University of Milan, San Donato Milanese, Milan, Italy; Laboratory of Muscle Histopathology and Molecular Biology, IRCCS Policlinico San Donato, San Donato Milanese, Milan, Italy.
| | - Rosanna Cardani
- Laboratory of Muscle Histopathology and Molecular Biology, IRCCS Policlinico San Donato, San Donato Milanese, Milan, Italy.
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Trivedi JR, Cannon SC, Griggs RC. Nondystrophic myotonia: challenges and future directions. Exp Neurol 2013; 253:28-30. [PMID: 24361411 DOI: 10.1016/j.expneurol.2013.12.005] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2013] [Revised: 11/27/2013] [Accepted: 12/10/2013] [Indexed: 12/29/2022]
Abstract
Non-dystrophic myotonias are rare diseases caused by mutations in skeletal muscle chloride and sodium ion channels with considerable phenotypic overlap between diseases. Common symptoms include muscle stiffness, transitory weakness, fatigue, and pain. Although seldom life-shortening, these myotonias cause life-time disability and affected individuals cannot perform many daily activities. A notable feature of the recessive form of chloride channelopathies is the presence of transient weakness. While there has been considerable progress in skeletal muscle channelopathies with regards to identifying biophysical abnormalities, the mechanism of transient weakness remains unclear. A recent study published in Experimental Neurology (Desaphy et al., 2013) explored this question further by comparing the biophysical properties of 3 chloride channel mutations associated with recessive myotonia congenita, with varying susceptibility to transient weakness. The authors identified a variety of functional defects in channel behavior among the 3 mutations, suggesting that this variability contributes to the differing phenotypes among chloride channelopathies. This commentary discusses nondystrophic myotonias, the results of Desaphy et al., and the treatment challenges in this rare disease.
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Affiliation(s)
- Jaya R Trivedi
- Department of Neurology and Neurotherapeutics, UT Southwestern Medical Center, Dallas, TX 75390, USA.
| | - Stephen C Cannon
- Department of Neurology and Neurotherapeutics, UT Southwestern Medical Center, Dallas, TX 75390, USA
| | - Robert C Griggs
- Department of Neurology, University of Rochester Medical Center, Rochester, NY, USA
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Kobeleva X, Petri S. Barriers to novel therapeutics in amyotrophic lateral sclerosis. Neurodegener Dis Manag 2013. [DOI: 10.2217/nmt.13.66] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
SUMMARY Amyotrophic lateral sclerosis is a devastating neurodegenerative condition primarily involving the motor system in the cerebral cortex, brain stem and spinal cord, but can, in later disease stages, also affect distinct extramotor brain regions. In this article, we discuss the prevalent barriers, including clinical and genetic variability of amyotrophic lateral sclerosis, frailty of the current mouse model and inadequateness of clinical trials, in the search for novel therapeutics. Approaches in terms of understanding the pathogenesis, and the search for biomarkers to initiate early or even presymptomatic treatment and monitor treatment effects are highlighted.
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Affiliation(s)
- Xenia Kobeleva
- Department of Neurology, Hannover Medical School, Carl-Neuberg-Straße 1, 30625 Hannover, Germany
| | - Susanne Petri
- Department of Neurology, Hannover Medical School, Carl-Neuberg-Straße 1, 30625 Hannover, Germany
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Heatwole CR, Statland JM, Logigian EL. The diagnosis and treatment of myotonic disorders. Muscle Nerve 2013; 47:632-48. [PMID: 23536309 DOI: 10.1002/mus.23683] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/14/2012] [Indexed: 12/12/2022]
Abstract
Myotonia is a defining clinical symptom and sign common to a relatively small group of muscle diseases, including the myotonic dystrophies and the nondystrophic myotonic disorders. Myotonia can be observed on clinical examination, as can its electrical correlate, myotonic discharges, on electrodiagnostic testing. Research interest in the myotonic disorders continues to expand rapidly, which justifies a review of the scientific bases, clinical manifestations, and numerous therapeutic approaches associated with these disorders. We review the pathomechanisms of myotonia, the clinical features of the dystrophic and nondystrophic myotonic disorders, and the diagnostic approach and treatment options for patients with symptomatic myotonia.
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Affiliation(s)
- Chad R Heatwole
- Department of Neurology, Box 673, University of Rochester Medical Center, 601 Elmwood Avenue, Rochester, New York, New York 14642, USA.
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Skalsky AJ, Oskarsson B, Han JJ, Richman D. Current pharmacologic management in selected neuromuscular diseases. Phys Med Rehabil Clin N Am 2012; 23:801-20. [PMID: 23137738 DOI: 10.1016/j.pmr.2012.09.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
For generations, the neuromuscular disorder care community has focused on establishing the correct diagnosis and providing supportive care. As the pathophysiology and genetics of these conditions became better understood, novel treatments targeting the disease mechanism were developed. This has led to some significant disease-modifying and supportive treatments for several neuromuscular disorders. The current treatments for amyotrophic lateral sclerosis (ALS), neuromuscular junction disorders, inflammatory myopathies, and myotonia are reviewed. Additionally, investigational treatments for ALS, Duchenne muscular dystrophy, and spinal muscular atrophy are discussed.
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Affiliation(s)
- Andrew J Skalsky
- Department of Pediatrics, Rady Children's Hospital San Diego, University of California San Diego, San Diego, CA 92123, USA.
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Statland JM, Bundy BN, Wang Y, Rayan DR, Trivedi JR, Sansone VA, Salajegheh MK, Venance SL, Ciafaloni E, Matthews E, Meola G, Herbelin L, Griggs RC, Barohn RJ, Hanna MG. Mexiletine for symptoms and signs of myotonia in nondystrophic myotonia: a randomized controlled trial. JAMA 2012; 308:1357-65. [PMID: 23032552 PMCID: PMC3564227 DOI: 10.1001/jama.2012.12607] [Citation(s) in RCA: 129] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
CONTEXT 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. DESIGN, SETTING, AND PARTICIPANTS 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. INTERVENTION 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. MAIN OUTCOME MEASURES 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. CONCLUSION 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. TRIAL REGISTRATION clinicaltrials.gov Identifier: NCT00832000.
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Affiliation(s)
- Jeffrey M Statland
- Department of Neurology, University of Rochester Medical Center, Rochester, NY
| | - Brian N Bundy
- Pediatrics Epidemiology Center, University of South Florida, Tampa, FL
| | - Yunxia Wang
- Department of Neurology, University of Kansas Medical Center, Kansas City, KS
| | - Dipa Raja Rayan
- MRC Centre for Neuromuscular Diseases, UCL Institute of Neurology, London, UK
| | - Jaya R Trivedi
- Department of Neurology, University of Texas Southwestern, Dallas, TX
| | - Valeria A Sansone
- Department of Neurology, University of Milan, IRCCS Policlinico San Donato, Milan, Italy
| | - Mohammad K Salajegheh
- Department of Neurology, Neuromuscular Division, Brigham and Women’s Hospital and Harvard Medical School, Boston, MA
| | - Shannon L. Venance
- Department of Clinical Neurological Sciences, London Health Sciences Centre, London, ON Canada
| | - Emma Ciafaloni
- Department of Neurology, University of Rochester Medical Center, Rochester, NY
| | - Emma Matthews
- MRC Centre for Neuromuscular Diseases, UCL Institute of Neurology, London, UK
| | - Giovanni Meola
- Department of Neurology, University of Milan, IRCCS Policlinico San Donato, Milan, Italy
| | - Laura Herbelin
- Department of Neurology, University of Kansas Medical Center, Kansas City, KS
| | - Robert C Griggs
- Department of Neurology, University of Rochester Medical Center, Rochester, NY
| | - Richard J Barohn
- Department of Neurology, University of Kansas Medical Center, Kansas City, KS
| | - Michael G Hanna
- MRC Centre for Neuromuscular Diseases, UCL Institute of Neurology, London, UK
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Statland JM, Wang Y, Richesson R, Bundy B, Herbelin L, Gomes J, Trivedi J, Venance S, Amato A, Hanna M, Griggs R, Barohn RJ. An interactive voice response diary for patients with non-dystrophic myotonia. Muscle Nerve 2011; 44:30-5. [PMID: 21674518 DOI: 10.1002/mus.22007] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
INTRODUCTION Non-dystrophic myotonia (NDM) is caused by mutations in muscle chloride and sodium channels. Currently, there is no standardized instrument for documenting symptom frequency and severity in NDM. METHODS Subjects used an automated, interactive, telephone-based voice response diary (IVR) to record frequency and severity of stiffness, weakness, pain, and tiredness once a week for 8 weeks, after their baseline visits. RESULTS We describe the IVR and report data on 76 subjects for a total of 385 person-weeks. Overall there were 5.1 calls per subject. Forty-eight subjects called in 5 or more times, and 14 called in 8 times. Stiffness was both the most frequent and severe symptom. Warm-up and handgrip myotonia were associated with higher severity scores for stiffness. CONCLUSIONS IVR is a convenient technology to allow patient reporting of repeated and real-time symptom frequency and severity, and it is presently being used in a trial of mexiletine in NDM.
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Affiliation(s)
- Jeffrey M Statland
- Department of Neurology, University of Rochester Medical Center, Rochester, New York, USA
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Conravey A, Santana-Gould L. Myotonia congenita and myotonic dystrophy: surveillance and management. Curr Treat Options Neurol 2011; 12:16-28. [PMID: 20842486 DOI: 10.1007/s11940-009-0055-z] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
OPINION STATEMENT Myotonia can be treated both pharmacologically and by lifestyle modifications. Cell membrane stabilizers are the medications most commonly used for symptomatic treatment of myotonia. Most patients do not require treatment for the myotonia itself, unless it is severe, but physicians must be aware of anesthesia risks in both myotonia congenita and myotonic dystrophy. A mainstay of management of myotonic dystrophy is the surveillance and treatment of its various systemic complications.
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Affiliation(s)
- Allison Conravey
- Department of Pediatrics, Tulane University, 1430 Tulane Avenue, SL-37, New Orleans, LA, 70112, USA,
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Fujii K, Iranami H, Hatano Y. Exacerbation of acetazolamide-responsive sodium channel myotonia by uterotonic agents. Int J Obstet Anesth 2011; 20:76-9. [DOI: 10.1016/j.ijoa.2010.07.014] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/21/2009] [Revised: 07/13/2010] [Accepted: 07/23/2010] [Indexed: 11/29/2022]
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Logigian EL, Martens WB, Moxley RT, McDermott MP, Dilek N, Wiegner AW, Pearson AT, Barbieri CA, Annis CL, Thornton CA, Moxley RT. Mexiletine is an effective antimyotonia treatment in myotonic dystrophy type 1. Neurology 2010; 74:1441-8. [PMID: 20439846 DOI: 10.1212/wnl.0b013e3181dc1a3a] [Citation(s) in RCA: 115] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
OBJECTIVE To determine if mexiletine is safe and effective in reducing myotonia in myotonic dystrophy type 1 (DM1). BACKGROUND Myotonia is an early, prominent symptom in DM1 and contributes to decreased dexterity, gait instability, difficulty with speech/swallowing, and muscle pain. A few preliminary trials have suggested that the antiarrhythmic drug mexiletine is useful, symptomatic treatment for nondystrophic myotonic disorders and DM1. METHODS We performed 2 randomized, double-blind, placebo-controlled crossover trials, each involving 20 ambulatory DM1 participants with grip or percussion myotonia on examination. The initial trial compared 150 mg of mexiletine 3 times daily to placebo, and the second trial compared 200 mg of mexiletine 3 times daily to placebo. Treatment periods were 7 weeks in duration separated by a 4- to 8-week washout period. The primary measure of myotonia was time for isometric grip force to relax from 90% to 5% of peak force after a 3-second maximum grip contraction. EKG measurements and adverse events were monitored in both trials. RESULTS There was a significant reduction in grip relaxation time with both 150 and 200 mg dosages of mexiletine. Treatment with mexiletine at either dosage was not associated with any serious adverse events, or with prolongation of the PR or QTc intervals or of QRS duration. Mild adverse events were observed with both placebo and mexiletine treatment. CONCLUSIONS Mexiletine at dosages of 150 and 200 mg 3 times daily is effective, safe, and well-tolerated over 7 weeks as an antimyotonia treatment in DM1. CLASSIFICATION OF EVIDENCE This study provides Class I evidence that mexiletine at dosages of 150 and 200 mg 3 times daily over 7 weeks is well-tolerated and effective in reducing handgrip relaxation time in DM1.
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Affiliation(s)
- E L Logigian
- Department of Neurology, University of Rochester, Rochester, NY, USA.
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Otten RF, Scherschel JA, Lopshire JC, Bhakta D, Pascuzzi RM, Groh WJ. Arrhythmia exacerbation after sodium channel blockade in myotonic dystrophy type 1. Muscle Nerve 2009; 40:901-2. [DOI: 10.1002/mus.21345] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Carocci A, Catalano A, Bruno C, Lentini G, Franchini C, De Bellis M, De Luca A, Conte Camerino D. Synthesis and in vitro sodium channel blocking activity evaluation of novel homochiral mexiletine analogs. Chirality 2009; 22:299-307. [DOI: 10.1002/chir.20741] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Avez-Couturier J, Michaud L, Cuisset JM, Lamblin MD, Dolhem P, Turck D, Vallée L, Gottrand F. Encoprésie révélatrice d’une dystrophie myotonique de Steinert : à propos de 2 observations. Arch Pediatr 2009; 16:430-4. [DOI: 10.1016/j.arcped.2009.02.018] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2008] [Revised: 09/05/2008] [Accepted: 02/05/2009] [Indexed: 11/30/2022]
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Abstract
INTRODUCTION Paramyotonia congenita is an autosomal dominant sodium channelopathy, caused by mutations in gene coding for muscle voltage-gated sodium channel alpha subunit. CASE REPORT We report the case of a 38-year-old man who described since childhood muscle stiffness with attacks ok weakness induced by two provocative stimuli: cold exposure and exercise. It primarily concerned eyelids and hands, occasionally limbs. Family history suggested an autosomal dominant mode of transmission. Clinical examination revealed myotonia at the thenar eminence percussion. Generalized myotonic discharges were observed on electromyography. Molecular diagnosis reported an Arg1448Cys mutation in exon 24 in gene coding for muscle voltage-gated sodium channel alpha subunit (SCN4A) in chromosome 17. CONCLUSION Paramyotonia congenita is not evolutive. Treatment is essentially preventive. Some medications could be proposed: membrane stabilizing agents like antiarrhythmic drugs (mexiletine, tocainide), or the carbonic anhydrase inhibitor (acetazolamide). Precautions may be taken during general anaesthesia because of diaphragm myotonia risk.
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Muraglia M, Franchini C, Corbo F, Scilimati A, Tortorella V, Sinicropi MS, De Luca A, De Bellis M, Camerino DC. Synthesis of beta-proline like derivatives and their evaluation as sodium channel blockers. J Heterocycl Chem 2007. [DOI: 10.1002/jhet.5570440519] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Abstract
The nondystrophic myotonias are a heterogeneous set of rare diseases that demonstrate clinical myotonia, electrical myotonia, or both. These disorders are distinguished from myotonic dystrophy type 1 (DM-1), the more recently described proximal myotonic myopathy/myotonic dystrophy type 2 (PROMM/DM-2), and proximal myotonic dystrophy (a variant of DM-2) by characteristic clinical features, lack of abnormal nucleotide repeat expansions in the DM-1 and DM-2 genes, lack of cataracts and endocrine disturbances, and absence of significant histopathology in the muscle biopsy. The present article reviews each of the nondystrophic myotonias by exploring the unique clinical features, electrodiagnostic findings, diagnostic criteria, gene mutations, and response to pharmacologic therapy. These diseases are divided into those with chloride channel dysfunction (the myotonia congenita disorders) and those with sodium channel dysfunction (paramyotonia congenita, potassium-aggravated myotonia, and hyperkalemic periodic paralysis with myotonia). The variants that occur in each of these conditions are commented on. The differentiating features of the nondystrophic myotonias are summarized, and their predominant clinical, electrodiagnostic, and genetic characteristics are tabulated. For a comprehensive review of pertinent research and studies with application to diagnosis and treatment of individuals with nondystrophic myotonic disorders, the present article is best read in the context of other articles in this issue, especially those on ion channel physiology (Cannon) and pharmacology (Conte-Camerino), and on hyperkalemic periodic paralysis (Lehmann-Horn).
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Affiliation(s)
- Chad R Heatwole
- Department of Neurology, University of Rochester, Rochester, New York, USA.
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Savitha MR, Krishnamurthy B, Hyderi A, Ramachandra NB. Myotonia congenita--a successful response to carbamazepine. Indian J Pediatr 2006; 73:431-3. [PMID: 16741331 DOI: 10.1007/bf02758569] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Myotonia congenita is a rare disease of skeletal muscle characterized by painless myotonia, generalized muscular hypertrophy and a non-progressive course. We report a 10-year-old girl with myotonia, "Herculean appearance" and electromyographic confirmation of myotonic discharges. There was a dramatic response to carbamazepine. The aim of this report is to make the readers aware of this entity which can be easily controlled with medication and also prevented by genetic counseling.
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Affiliation(s)
- M R Savitha
- Department of Pediatrics, Government Medical College, Mysore, India.
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Aoike F, Takahashi MP, Sakoda S. Class Ic antiarrhythmics block human skeletal muscle Na channel during myotonia-like stimulation. Eur J Pharmacol 2006; 532:24-31. [PMID: 16473348 DOI: 10.1016/j.ejphar.2005.12.021] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2005] [Revised: 11/30/2005] [Accepted: 12/12/2005] [Indexed: 10/25/2022]
Abstract
Flecainide, a class Ic antiarrhythmic drug, has been anecdotally reported to improve myotonia, but little is known about its kinetics on human skeletal muscle sodium channels applicable in vivo. Here we explored the anti-myotonic action of flecainide for human skeletal muscle sodium channels heterologously expressed in cultured cells. Flecainide blocked sodium channels in a highly state-dependent manner with 20-fold difference in IC(50) between use-dependent and tonic blocks. When pulses of brief depolarization simulating myotonia were applied from a holding potential of -90 mV, flecainide at therapeutic concentrations significantly blocked sodium currents. Flecainide slowed the time course of recovery but most channels recovered from block within 10-20 s. In contrast to mexiletine, flecainide did not markedly block sodium current during prolonged depolarization, suggesting an open-channel blocking action. Considering the slow recovery from block and the specific action against repetitive depolarization, flecainide may represent a potent therapeutic agent for myotonia.
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Affiliation(s)
- Futoshi Aoike
- Department of Neurology, Osaka University Graduate School of Medicine D-4, 2-2 Yamadaoka, Suita, Osaka 565-0871, Japan
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Abstract
BACKGROUND Abnormal delayed relaxation of skeletal muscles, known as myotonia, can cause disability in myotonic disorders. Sodium channel blockers, tricyclic antidepressive drugs, benzodiazepines, calcium-antagonists, taurine and prednisone may be of use in reducing myotonia. OBJECTIVES To consider the evidence from randomised controlled trials on the efficacy and tolerability of drug treatment in patients with clinical myotonia due to a myotonic disorder. SEARCH STRATEGY We searched the Cochrane Neuromuscular Disease Group trials register (April 2004), MEDLINE (January 1966 to December 2003) and EMBASE (January 1980 to December 2003). Grey literature was handsearched and reference lists of identified studies and reviews were examined. Authors, disease experts and manufacturers of anti-myotonic drugs were contacted. SELECTION CRITERIA We considered all (quasi) randomised trials of participants with myotonia treated with any drug treatment versus no therapy, placebo or any other active drug treatment. The primary outcome measure was:reduced clinical myotonia using two categories: (1) no residual myotonia or improvement of myotonia or (2) No change or worsening of myotonia. Secondary outcome measures were:(1) clinical relaxation time; (2) electromyographic relaxation time; (3) stair test; (4) presence of percussion myotonia; and (5) proportion of adverse events. DATA COLLECTION AND ANALYSIS Two authors extracted the data independently onto standardised extraction forms and disagreements were resolved by discussion. MAIN RESULTS Nine randomised controlled trials were found comparing active drug treatment versus placebo or another active drug treatment in patients with myotonia due to a myotonic disorder. Included trials were double-blind or single-blind crossover studies involving a total of 137 patients of which 109 had myotonic dystrophy type 1 and 28 had myotonia congenita. The studies were of poor quality. Therefore, we were not able to analyse the results of all identified studies. Two small crossover studies without a washout period demonstrated a significant effect of imipramine and taurine in myotonic dystrophy. One small crossover study with a washout period demonstrated a significant effect of clomipramine in myotonic dystrophy. Meta-analysis was not possible. AUTHORS' CONCLUSIONS Due to insufficient good quality data and lack of randomised studies, it is impossible to determine whether drug treatment is safe and effective in the treatment of myotonia. Small single studies give an indication that clomipramine and imipramine have a short-term beneficial effect and that taurine has a long-term beneficial effect on myotonia. Larger, well-designed randomised controlled trials are needed to assess the efficacy and tolerability of drug treatment for myotonia.
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Affiliation(s)
- J Trip
- Academisch Ziekenhuis Maastricht (AZM), Department of Neurology, P. Debyelaan 25 Postbus5800, Maastricht, Limburg, Netherlands, 6202 AZ.
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Abstract
OBJECTIVE In order to find some appropriate medicine to suppress myotonia without decreasing muscle strength experiments were performed on myotonic (mto) mice whose Cl channel does not develop due to stop codon and serves as an animal model of myotonia. In myotonic dystrophy dehydroepiandrosterone is low in the serum and it has been reported that intravenous injections of DHEAS to human cases improves myotonia and activities of daily living. MATERIALS AND METHODS Three pairs of heterozygote mto mice, SWR/J-Clcn1(adr-mto/+) and ten Wistar rats were used. We performed intracellular recordings of myotonia from mto mice and the drug effects on insertion myotonia were recorded from the hemidiaphragm preparations of mto mice with different concentrations of DHEAS. Isometric twitch tension was recorded from rat hemidiaphragm preparations in Tyrode's solution and the effect of DHEAS on the muscle twitch tension was measured at different concentrations of DHEAS from 100 mg/l to 300 mg/l. The effect of mexiletine on ITT was also measured. RESULTS In mto mice insertion myotonia was recorded as soon as the microelectrode was inserted in the muscle cells. When DHEAS was added to Tyrode's solution, insertion myotonia was suppressed. DHEAS decreased ITT up to 70% of the original value, though mexiletine decreased ITT to 30% of the original value. Therefore, the decrement of the muscle strength in DHEAS solution is much smaller than that of mexiletine. CONCLUSION Since myotonic dystrophy shows progressive muscle weakness in addition to myotonia, medications like DHEAS are more favorable than the typical Na channel blocker.
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Affiliation(s)
- Hiroshi Nakazora
- Division of Neurology, Department of Internal Medicine, Toho University Ohashi Medical Center, Tokyo, Japan
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Abstract
A variety of inherited human disorders affecting skeletal muscle contraction, heart rhythm, and nervous system function have been traced to mutations in genes encoding voltage-gated sodium channels. Clinical severity among these conditions ranges from mild or even latent disease to life-threatening or incapacitating conditions. The sodium channelopathies were among the first recognized ion channel diseases and continue to attract widespread clinical and scientific interest. An expanding knowledge base has substantially advanced our understanding of structure-function and genotype-phenotype relationships for voltage-gated sodium channels and provided new insights into the pathophysiological basis for common diseases such as cardiac arrhythmias and epilepsy.
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Affiliation(s)
- Alfred L George
- Division of Genetic Medicine, Department of Medicine, Vanderbilt University, Nashville, Tennessee 37232-0275, USA.
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Kongenitale myotone Dystrophie. Monatsschr Kinderheilkd 2005. [DOI: 10.1007/s00112-003-0862-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Hwang WJ, Tsai JJ. Acute phenytoin intoxication: causes, symptoms, misdiagnoses, and outcomes. Kaohsiung J Med Sci 2005; 20:580-5. [PMID: 15696787 DOI: 10.1016/s1607-551x(09)70262-1] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022] Open
Abstract
Phenytoin is a commonly prescribed antiepileptic drug. Due to its saturation (zero-order) pharmacokinetics, phenytoin carries a special risk of dose-related toxicity that is an important issue in emergency medicine. The purpose of this cross-sectional case-series study was to investigate the causes, symptoms, misdiagnoses, and outcomes of acute phenytoin intoxication. It was based on a retrospective chart review of 30 inpatients (mean age, 41.6 +/- 22.8 years) with 36 episodes of acute phenytoin intoxication at our university hospital in the past 13 years. The average initial serum phenytoin level was 47.3 +/- 9.7 microg/mL (range, 27.9-70.4 microg/mL). Excessive self-medication, misunderstanding of the prescription order, and probable drug interaction were the three leading causes of acute phenytoin intoxication. Unsteady gait, dizziness/vertigo, nausea/vomiting, general weakness, and drowsiness were the most common presenting symptoms. The tentative diagnostic accuracy was 67%. The most common initial misdiagnosis was brainstem or cerebellum stroke (14%). The clinical course in all patients was uneventful under temporary withdrawal of phenytoin and supportive care. We concluded that acute phenytoin intoxication was relatively under-diagnosed in the emergency service. Although acute phenytoin intoxication causes no mortality and has a good outcome, the unsteady gait increases the risk of injuries caused by falls. The management of acute phenytoin intoxication includes temporary withdrawal of phenytoin and supportive care.
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Affiliation(s)
- Wen-Juh Hwang
- Department of Neurology, College of Medicine, National Cheng Kung University, Tainan, Taiwan
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