Drug-induced myotonia

**Definition:** Drug-induced myotonia refers to the myotonia-inducing effects of certain drugs. Hypocholesterolaemic agents may induce myotonia by altering the sterol composition of the muscle cell membrane, while other drugs including beta-adrenergic blockers and agonists, succinylcholine and diuretics may exacerbate or unmask pre-existing myotonia.

**Exclusions:** - Myasthenia gravis or certain specified neuromuscular junction disorders - Secondary myopathies