Clozapine, an atypical neuroleptic agent with D 4 receptor antagonist activity, does not cause tardive dyskinesia but may cause agranulocytosis.
This is of potential clinical importance for products with a narrow therapeutic window, e.g. theophylline, clozapine and ropinirole.
A major breakthrough in the treatment of schizophrenia occurred in 1990 with the introduction of the drug clozapine to the U.S. market.
However, even clozapine does not work for all patients.