atypical antipsychotic
a class of antipsychotic drugs used in the treatment of schizophrenia, delusional disorders, and other disorders characterized by psychotic symptoms, including psychotic bipolar mania. Atypical antipsychotics are also used to treat aggression associated with autism and as adjunctive agents in the treatment of some nonpsychotic conditions, such as obsessive-compulsive disorder, explosive disorder, and severe depression. They are dopamine-receptor antagonists and also block the effects of serotonin at 5-HT2A receptors. They have additional actions at other neurotransmitter receptors but are not identical in these additional actions. The prototype of the group is clozapine; others in current clinical use include aripiprazole, asenapine, iloperidone, lurasidone, olanzapine, quetiapine, risperidone, and ziprasidone. Compared with conventional (typical or
first-generation) antipsychotics, atypical antipsychotics produce fewer extrapyramidal symptoms, are less likely to alter serum levels of prolactin, and appear to be less likely to cause tardive dyskinesia, all of which are significant adverse effects of the conventional drugs. However, they have been associated with metabolic effects, such as obesity, diabetes, and high cholesterol. In addition, extreme hyperglycemia, sometimes associated with diabetic ketoacidosis or hyperosmolar coma or death, has been reported. Clozapine use is also associated with agranulocytosis; later atypical antipsychotics (e.g., olanzapine) do not have this side effect. Also called novel antipsychotic; second-generation antipsychotic.