the US FDA in 2009, it is fairly well tolerated, although hypotension, dizziness, and somnolence were very common side effects. Has not received regulatory approval in other countries, however. Paliperidone – Primary, active metabolite of risperidone that was approved in 2006. Perospirone † – Has a higher incidence of extrapyramidal side effects than other atypical antipsychotics. Risperidone – Divided dosing is recommended until initial titration is completed, at which time the drug can be administered once daily. Used off-label to treat Tourette syndrome and anxiety disorder. Ziprasidone – Approved in 2004 to treat bipolar disorder. Side-effects include a prolonged QT interval in the heart, which can be dangerous for patients with heart disease or those taking other drugs that prolong the QT interval. Butyrophenones Melperone † – Only used in a few European countries. No English-speaking country has licensed it to date. Lumateperone Tricyclics Asenapine – Used for the treatment of schizophrenia and acute mania associated with bipolar disorder. Clozapine – Requires routine laboratory monitoring of complete blood counts every one to four weeks due to the risk of agranulocytosis. It has unparalleled efficacy in the treatment of treatment-resistant schizophrenia. Olanzapine – Used to treat psychotic disorders including schizophrenia, acute manic episodes, and maintenance of bipolar disorder. Used as an adjunct to antidepressant therapy, either alone or in combination with fluoxetine as Symbyax. Quetiapine – Used primarily to treat bipolar disorder and schizophrenia. Also used and licensed in a few countries (including Australia, the United Kingdom and the United States) as an adjunct to antidepressant therapy in patients with major depressive disorder. It's the only antipsychotic that's demonstrated efficacy as a monotherapy for the treatment of major depressive disorder. It indirectly serves as a norepinephrine reuptake inhibitor by means of its active metabolite, norquetiapine. Zotepine – An atypical antipsychotic indicated for acute and chronic schizophrenia. It is still used in Japan and was once used in Germany but it was discontinued.† Others Blonanserin – Approved by the PMDA in 2008. Used in Japan and South Korea. Pimavanserin – A selective 5-HT2A receptor antagonist approved for the treatment of Parkinson's disease psychosis in 2016. Sertindole ‡ – Developed by the Danish pharmaceutical company H. Lundbeck. Like the other atypical antipsychotics, it is believed to have antagonist activity at dopamine and serotonin receptors in the brain. Third-generation Third generation antipsychotics are recognized as demonstrating D2 receptor agonism as opposed to the D2