Quetiapine is a dibenzothiazepine atypical antipsychotic agent. Its 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.
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.