In patients with mild clinical symptoms, drug treatment is often unnecessary.

Life style

  • Relaxation techniques and stress avoiding (well known provocative factor) are beneficial
  • Avoiding periods of longer rest or maintenance of same position helps with muscle stiffness control
  • Sudden movements after prolonged rest should be avoided in order to prevent muscle injuries and falls
  • Warm up phenomenon
  • Exercise and stretching is recommended to improve flexibility, especially in Achilles tendons which frequently require surgical lengthening

 Drug treatment


  • Mexiletine is most often the first choice for treatment of myotonia, based on its efficacy and mostly benign adverse effect profile. It is a antiarrhythmic agent, which acts on fast-acting voltage-gated sodium channels. Its half-life is 10 to 12 h.
  • Standard dosage is 150 mg to 200 mg  in adults and 1 to 8 mg/kg per day given two to three times a day given with meal in order to prevent gastrointestinal side-effects.
  • Treatment starts with lowe dose which increases over time. Patients are advised to stop tretament every few years to sure that treatment is still warranted
  • Because rapid discontinuation can cause a rebound in myotonia and stiffness, the drug should be tapered in 50-mg increments every few days.
  • Contraindications: patients with severe cardiac arrhythmias, cardiomyopathy, or coronary artery disease. It should also not be used in patients with an allergic response to lidocaine or lidocaine derivatives
  • Side-effects: epigastric symptoms (20% of patients) that can be alleviated if the drug is taken with food, lightheadedness (10%,), skin rash (3%). Other side-effects are anxiety, headaches, and coordination difficulties.


  • Tocainide is a lidocaine derivative that acts on the sodium channel. It has been shown to be as effective as mexiletine in controlling myotonia. However, because it has a depressive effect on bone marrow, it is considered a second-line agent for the treatment of myotonia congenita. Its half-life is 15 h.
  • Standard dosage is 200 mg twice a day. It can be increased up to 1,200 to 1,600 mg/d divided in two or three doses
  • Contraindications: patients with severe cardiac arrhythmias, cardiomyopathy, or coronary artery disease and patients allergic to lidocaine and its derivates. Tocainide should be avoided in any patient with a history of bone marrow suppression.
  • Side effects: dizziness (11%), lymphadenopathy (3%), nausea, anxiety, and tremor.


  • Carbamazepine works by reducing post-tetanic potentiations and is thought to stabilize the muscle membrane. Its half-life is 12 to 17 h.
  • Contraindications: hypersensitivity to tricyclic antidepressants or a history of recent use of monoamine oxidase inhibitors. It also should be avoided in patients with a history of increased intraocular pressure, liver and kidney disease
  • Side effects : somnolence, changes in ECG, dizziness, blurred vision, lack of coordination, increased liver enzymes


  • Phenytoin works as voltage-dependent sodium and calcium channel modulator

Drugs to avoid

  • Beta-agonists, beta-blockers, acetilcholiesterase inhibitors – worsen myotonia
  • Colchicin- causes muscle weakness

 Anesthesia in patients with myotonia

  • Patients with congenital myotonia have an increased risk for development of malignant hyperthermia
  • Suxamethonium, succinylcholine, and propofol can induce myotonia
  • It should be taken into consideration that patients should be kept warm during surgery
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Myotonia Congenita

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