Baclofen-induced dyskinesia.

Baclofen (Lioresal) is a derivative of the inhibitory neurotransmitter gamma-aminobutyric acid (GABA). It is used to treat spasticity particularly for the relief of flexor spasms, pain, clonus, and muscular rigidity. There have been many rare neurologic side effects reported with its use. These side effects, in particular, hallucinations and seizures, have been observed predominantly following precipitous withdrawal of the drug. We present a case demonstrating a muscular dyskinetic side effect when baclofen treatment was first initiated. The mechanism by which baclofen affects spasticity and how the resulting side effect of dyskinesia developed in our patient is not known. They are, however, most probably related to dopamine receptor hypersensitivity and the resulting imbalance of the dopaminergic/cholinergic systems. Clinicians should be aware of this additional adverse effect of muscular dyskinesia, with the use of baclofen, and its reversibility when baclofen is discontinued.