tardive dyskinesia
a movement disorder associated with the use of antipsychotics, particularly conventional antipsychotics that act primarily as dopamine-receptor antagonists. It is more common with prolonged use (months or years), and older patients, females, and patients with mood disorders are thought to be more susceptible. Symptoms include tremor, so-called choreoathetoid movements (see choreoathetosis), and spasticity of muscle groups, particularly orofacial muscles and muscles in the extremities. Onset is insidious and may be masked by continued use of the antipsychotic, only appearing when the drug is discontinued or the dose lowered. Its incidence is estimated at up to 40% of long-term users of conventional antipsychotics; the incidence is lower with atypical antipsychotics. No effective treatment is known.