A dibenzothiazepine atypical antipsychotic agent, Quetiapine's clinical antipsychotic properties and low extrapyramidal side effect is mediated through a combination of D2 and 5-HT2 receptor antagonism. It has high affinity at histaminergic H1 and adrenergic α1 receptors, moderate affinity at adrenergic α2 receptors, and moderate to high affinity at several antimuscarinic receptors.

Adult
PO
Schizophrenia: 25 mg bid on day 1, increased to 50 mg bid on day 2, 100 mg bid on day 3, and 150 mg bid on day 4. Usual range: 300-450 mg/day in 2 divided doses. Max: 750 mg/day.
Acute manic episodes of bipolar disorder: 50 mg bid on day 1, 100 mg bid on day 2, 150 mg bid on day 3, and 200 mg bid on day 4. Usual range: 400-800 mg/day in 2 divided doses. Max: 800 mg/day.
Depressive phase of bipolar disorder: 50 mg at bedtime on day 1, 100 mg on day 2, 200 mg on day 3, and 300 mg on day 4. Usual dose: 300 mg/day. Max: 600 mg/day.
Prophylaxis of bipolar disorder: Continue therapy at the dose effective for treatment of bipolar disorder; adjust dose depending on clinical response and tolerability w/in 300-800 mg bid. Use lowest effective dose for maintenance therapy.

Adverse drug reactions: somnolence, headache, dizziness, weight gain, rises in plasma-triglyceride and total cholesterol concentrations; mild asthenia, anxiety, irritability, fever, raised liver enzyme values; orthostatic hypotension associated w/ dizziness, QT-interval prolongation.

Adapted from CIMS Drug Information System. Internet. Accessed on January 10, 2016.