clozapine
n. an atypical antipsychotic agent of the dibenzodiazepine class: the first of the atypical antipsychotics to be used clinically and released into the U.S. market in 1990. Although regarded by some as the most effective of all antipsychotic drugs, clozapine has problematic side effects that have limited its use. Among others, these adverse effects may include weight gain, sedation, and—importantly—agranulocytosis, which may occur in 1% to 2% of patients treated with the drug. Use of clozapine therefore requires frequent monitoring of white blood cell counts in patients and is generally reserved for patients who have responded suboptimally to other antipsychotic agents. U.S. trade name: Clozaril.