n. an atypical antipsychotic used for the management of psychosis and schizophrenia. As with conventional antipsychotics, its therapeutic effects are in part related to its ability to block D2 dopamine receptors (see dopamine-receptor antagonist); however, it differs from the older agents in its ability to also block 5-HT2serotonin receptors. It is also approved for treatment of bipolar disorder and (in its extended-release formulation) as an adjunct to antidepressant drugs for unipolar depression. Sedation is a common adverse effect; thyroid dysfunction, weight gain, and electrocardiographic effects are more rarely observed. U.S. trade name: Seroquel.