DRD2 and schizophrenia: The main drugs currently used for psychosis and schizophrenia are the dopamine D2 receptor antagonist, such as haloperidol, risperidone, or clozapine; serotonin 5-HT2A receptor antagonist, such as olanzapine or risperidone; or NMDA antagonists, like phencyclidine or ketamine.