Myotonia is a functional limiting symptom where the muscle stiffens on action leading to
arrest of movement. Pharmacological treatment may make the difference between a physically
restricted and a normal life. Today, patients with myotonia are treated with Mexiletine a
medications resulting in adverse events up to 40 % and which very expensive and difficult to
obtain.
Our clinic has, forced by the above problems related to Mexiletine, treated a few patients
with the drug Lamotrigine with pronounced positive effect in all. Lamotrigine belongs to the
same category of drugs as Mexiletine but has fewer and milder side effects. Based on the
similarities of the 2 drugs in pharmacological action and the positive experiences
investigators are convinced that Lamotrigine will show a positive effect if evaluated in a
broader scale. Due to the advantages of Lamotrigine compared to Mexiletine investigators find
it of outmost importance for patients that this drug is assessed formally to establish
Lamotrigine as a treatment choice for myotonia. Investigators believe that this will
potentially make a huge difference in life quality for persons with myotonia. Investigators
aim at investigating the efficacy and tolerability of Lamotrigine in the treatment of
myotonia in a randomized doublet blinded placebo controlled crossover study.