HALF-LIFE: Quetiapine 6-7 hours; Norquetiapine (active metabolite) STARTING DOSE: IR: 25mg-50mg PO BID; XR: 300mg PO QHS TARGET DOSING RANGE: 50mg-800mg daily BEST TIME TO DOSE: Bedtime HOW TO DOSE: >> IR: Initial 25mg-50mg PO BID. Increase by 50mg-100mg per day every 1-4 days. >> XR: Initial 150mg-300mg PO QHS. Increase by 150mg-300mg per day every 2-7 days. >> Max dose 800mg/day (some patients may require doses of up to 1200mg/day) PREGNANCY: Minimal data on safety. BREASTFEEDING: Minimal data on safety. FDA INDICATIONS: 1) Schizophrenia, 13yo and older 2) Bipolar disorder (manic/mixed), 10yo and older 3) Bipolar depression 4) Adjunctive treatment in Unipolar Major Depression
ADDITIONAL INFORMATION
Norquetiapine is the active metabolite of quetiapine and has antagonist effects at NET (norepinephrine transporter), 5HT7, 5HT2C, and α2 receptors as well as partial agonist effects at 5HT1A receptors
Different Drug Formulations
(IR): 300mg dose peaks to 90% D2 occupancy then rapidly declines
(IR): 800mg dose only occupies D2 at >60% for 12 hours
(XR): 300mg dose peaks slowly to 80% after 6 hours and stays above 60% for another 6 hours
(XR): 800mg dose fully effective D2 occupancy for 24 hours with less peak sedation
Quetiapine is a different drug at different doses
Hypnotic (H1) dose: 50mg
Antidepressant (5HT2C, NET) dose: 300mg
Antipsychotic (D2) dose: 800mg
Very Low EPS Risk
Very low risk for prolactin elevation
Weak D2 antagonism makes quetiapine a preferred antipsychotic for Parkinson’s (although pimavanserin is a better option)
Weight Gain is common due to antagonism at H1 and 5HT2C receptors
Sedation is common due to antagonism at α1 and H1 receptors
Orthostatic hypotension is common due to antagonism at α1 receptors
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