Clozapine: neuroleptic-induced EPS and tardive dyskinesia.

Clozapine has had a uniquely favorable motor system side effect profile since its initial evaluations. This has been convincingly corroborated by many double blind, single blind, and open studies treating acute and chronic psychosis. The acute extrapyramidal syndromes of dystonia, akathisia and parkinsonism infrequently occur, whereas these syndromes develop in up to 75% of patients receiving traditional neuroleptics. Tardive dyskinesia can be suppressed with higher doses of clozapine given over extended periods. However, an antipsychotic effect can be achieved in many patients at doses below the dyskinesia suppressing level. There is no established causative relationship between clozapine and tardive dyskinesia, but there is a theoretical basis that this may occur. Preliminary data suggest clozapine has mild antiparkinsonian effects as well as efficacy in controlling dopamine agonist-induced psychosis without aggravating parkinsonism. A much wider use of clozapine will further characterize the magnitude of differences compared to other neuroleptics, and identify additional indications for this special compound.