Educational only — not medical advice. If you’re in crisis or thinking about suicide: call or text 988 (U.S.) or your local emergency number. Support resources. Under construction and review—see the updates log.

quetiapine

Antipsychotic

Brand: SEROQUEL

Published 2025-09-16 · Last reviewed 2025-09-23 · 5 references

Content sourced from FDA labeling (DailyMed) and peer-reviewed literature.

Print sheet Review evidence

At a glance

Class: Antipsychotic·Typical dose: Schizophrenia (IR): day 1 25 mg BID, titrate to 300–400 mg/day by day 4; maintenance 300–800 mg/day divided BID.·Half-life: Steady-state mean 6 h·LAI available: No

Class: Antipsychotic
Typical dose: Schizophrenia (IR): day 1 25 mg BID, titrate to 300–400 mg/day by day 4; maintenance 300–800 mg/day divided BID.
Half-life: Steady-state mean 6 h
LAI available: No

Quick answers

What is quetiapine?: Quetiapine (Seroquel/Seroquel XR) is a second-generation antipsychotic approved for schizophrenia, bipolar I acute mania (monotherapy and adjunct), bipolar depression, and maintenance with lithium or divalproex, with both IR and XR tablets broadly available as generics.
What is SEROQUEL?: SEROQUEL is a brand name for quetiapine.
What is SEROQUEL (quetiapine) used for?: Label indications include: Schizophrenia; acute manic/mixed episodes; bipolar depression; adjunct for major depressive disorder.
What drug class is SEROQUEL (quetiapine)?: Atypical Antipsychotic.
What is the mechanism of action of SEROQUEL (quetiapine)?: Antagonist at 5‑HT2A and D2 (transient), strong H1 and alpha‑1 activity.
What strengths does SEROQUEL (quetiapine) come in?: Immediate-release tablets: 25, 50, 100, 200, 300, 400 mg; extended-release tablets: 50, 150, 200, 300, 400 mg.
Is SEROQUEL (quetiapine) a controlled substance?: No — it is not scheduled as a controlled substance under U.S. federal law.
What is SEROQUEL (quetiapine) dosing for schizophrenia?: Schizophrenia (IR): day 1 25 mg BID, titrate to 300–400 mg/day by day 4; maintenance 300–800 mg/day divided BID.
What is the maximum recommended dose of SEROQUEL (quetiapine)?: Maximum recommended dose for schizophrenia or mania is 800 mg/day; doses above this provide little added efficacy but increase metabolic and sedation burden.
What is the maximum dose of SEROQUEL (quetiapine) for major depressive disorder (clinical depression)?: Adjunct MDD: XR 150–300 mg nightly after gradual titration; reassess benefit within 4–8 weeks.

General information

Quetiapine (Seroquel/Seroquel XR) is a second-generation antipsychotic approved for schizophrenia, bipolar I acute mania (monotherapy and adjunct), bipolar depression, and maintenance with lithium or divalproex, with both IR and XR tablets broadly available as generics.

Its mechanism blends rapidly dissociating D2 antagonism with strong 5-HT2A/5-HT2C blockade plus H1 and α1 antagonism, explaining its low EPS risk, antidepressant properties, and characteristic sedation and orthostasis.

Clinicians favor quetiapine for its low EPS liability, antidepressant activity in bipolar disorder, and sedating properties, but metabolic burden, orthostatic hypotension, and potential misuse at low doses necessitate close monitoring.

The compare view and the Quetiapine evidence feed can help weigh metabolic load, sedation, and prolactin risk, alongside the bipolar disorder hub when planning mood disorder regimens.

U.S. approvals

Schizophrenia (adults) (1997)
Schizophrenia (adolescents 13–17) (2006)
Bipolar I mania (adults) (2004)
Bipolar I mania (pediatrics 10–17) (2009)
Bipolar depression (adults) (2008)
Bipolar depression (pediatrics 10–17) (2009)
Bipolar maintenance adjunct (2009)

Formulations & strengths

Immediate-release tablets: 25, 50, 100, 200, 300, 400 mg; extended-release tablets: 50, 150, 200, 300, 400 mg.

Generic availability

IR and XR generics have been widely available since 2012.

CATIE data indicate comparable antipsychotic effectiveness but higher discontinuation for weight gain versus some peers—reinforce metabolic surveillance and lifestyle counselling.

View labelExact

Mechanism of action

Refer to the Glossary entry on Neurotransmitters for background on receptor systems involved in serious mental illness.

Moderate-affinity dopamine D2 antagonism with rapid dissociation delivers antipsychotic efficacy while keeping striatal occupancy below the EPS threshold.

Serotonin 5-HT2A/5-HT2C blockade plus norquetiapine’s norepinephrine transporter inhibition and 5-HT1A partial agonism underpin antidepressant effects; strong H1 and α1 antagonism drives sedation and orthostasis.

D2/D3 and 5-HT2A/5-HT2C antagonism.
Norquetiapine: partial 5-HT1A agonist and norepinephrine transporter inhibitor.
High histamine H1 and adrenergic α1 antagonism; modest muscarinic activity through norquetiapine.

Metabolism & pharmacokinetics

Oral bioavailability ~9%; IR Tmax ~1.5 h, XR ~6 h with up to 50% higher exposure when taken with high-fat meals—advise consistent administration relative to food.
Approximately 83% protein bound; volume of distribution ~10 L/kg.
Extensively metabolized by CYP3A4 to multiple metabolites including active norquetiapine; CYP2D6 plays a minor role.
Half-life ~6–7 h for quetiapine and ~12 h for norquetiapine; <1% of a dose is excreted unchanged in urine.

Dosing & administration

Schizophrenia (IR): day 1 25 mg BID, titrate to 300–400 mg/day by day 4; maintenance 300–800 mg/day divided BID.
Schizophrenia (XR): start 300 mg nightly, increase to 600 mg on day 2; adjust to 400–800 mg once nightly with consistent food timing.
Bipolar I acute mania: titrate to 400–800 mg/day by day 4 (IR divided or XR nightly); combination with lithium/divalproex improves response but heightens sedation.
Bipolar depression: XR 50 mg day 1, 100 mg day 2, 200 mg day 3, 300 mg nightly thereafter (150 mg for sensitive or older adults).
Adjunct MDD: XR 150–300 mg nightly after gradual titration; reassess benefit within 4–8 weeks.
Hepatic impairment or frail/elderly patients: initiate 25 mg/day (IR) or 50 mg every other day (XR) and titrate by 25–50 mg/day with orthostatic monitoring; retitrate if ≥1 week of doses are missed.
Maximum recommended dose for schizophrenia or acute mania is 800 mg/day; doses beyond this threshold increase metabolic and sedation burden without clear efficacy gains.

Adverse effects

FDA boxed warnings

Class boxed warning for increased mortality in elderly patients with dementia-related psychosis.
Suicidal thoughts and behaviors in children, adolescents, and young adults for the bipolar depression indication.

Common side effects (≥10%)

Sedation/somnolence: Dose-related; counsel on evening dosing and driving precautions.
Weight gain: ≥7% body weight increase in 15–23% over 6 months—monitor BMI and waist circumference.
Dizziness/orthostasis: Advise slow position changes during titration.
Dry mouth: Encourage hydration and oral hygiene.
Constipation: Consider prophylactic bowel regimen, especially at higher doses.

Other notable effects

Metabolic syndrome (hyperglycemia, dyslipidemia) requires scheduled labs and lifestyle counselling.
Norquetiapine contributes to anticholinergic effects; monitor for urinary retention and gastrointestinal hypomotility.
EPS and tardive dyskinesia remain possible—perform abnormal involuntary movement exams periodically.
Cataract risk signal from animal studies—consider baseline and periodic eye exams for long-term therapy.
QT prolongation is usually mild but obtain ECGs when combining with other QT-active agents or in cardiac disease.

Interactions

Strong CYP3A4 inhibitors (e.g., ketoconazole, ritonavir) markedly increase exposure—avoid or reduce to ≤1/6th of the usual dose with intensive monitoring.
Strong CYP3A4 inducers (e.g., carbamazepine, phenytoin, rifampin, St. John’s wort) sharply reduce levels—avoid or select an alternative antipsychotic.
Lithium or divalproex combinations increase sedation, tremor, and weight gain—monitor closely.
Additive hypotension occurs with antihypertensives and α1 blockers; check blood pressure during titration.
Avoid grapefruit products and limit alcohol and other CNS depressants to reduce oversedation.

Other useful information

Schedule metabolic monitoring at baseline, 3 months, 6 months, and annually; escalate sooner if weight gain ≥5% or hyperglycemia emerges.
Educate patients not to crush or chew XR tablets and to take them consistently with or without food.
Counsel on morning orthostasis and evening sedation; advise gradual position changes, hydration, and consider bedtime dosing when daytime impairment persists.
Assess for misuse when prescribing low-dose IR for sleep; reinforce appropriate indications.
Taper gradually to prevent withdrawal insomnia and relapse; restart titration if therapy lapses for ≥1 week.
Use the compare view to balance metabolic, prolactin, and sedation profiles when selecting or switching SGAs.
Coordinate bipolar care plans with the bipolar disorder hub to integrate psychotherapy, lab monitoring, and relapse-prevention strategies.
Consider baseline and periodic eye exams during long-term therapy to address historical cataract concerns.

References

Related hubs:Schizophrenia hub·Bipolar hub