Seroquel (Quetiapine)
quetiapine fumarate · also available as Seroquel XR (extended-release)
Indications
| Indication | Approved Population | Therapy Type | Status |
|---|---|---|---|
| Schizophrenia | Adults; adolescents 13–17 years | Monotherapy | FDA Approved |
| Bipolar I disorder — manic episodes | Adults; children/adolescents 10–17 years | Monotherapy or adjunct to lithium/divalproex | FDA Approved |
| Bipolar disorder — depressive episodes | Adults | Monotherapy | FDA Approved |
| Bipolar I disorder — maintenance | Adults | Adjunct to lithium or divalproex | FDA Approved |
| MDD — adjunctive treatment (XR only) | Adults | Adjunctive to antidepressant | FDA Approved |
Quetiapine is one of the most broadly indicated atypical antipsychotics, with FDA approvals spanning schizophrenia, bipolar mania (monotherapy and adjunctive), bipolar depression, bipolar maintenance, and adjunctive treatment of MDD (XR formulation only, approved 2009). Its multi-receptor pharmacology — involving serotonin 5-HT2A, dopamine D2, histamine H1, and adrenergic alpha-1 receptor antagonism — underlies this range of indications. Quetiapine is not approved for dementia-related psychosis, and its use in elderly patients with dementia carries a boxed warning for increased mortality.
Generalised anxiety disorder: Three RCTs support quetiapine XR monotherapy for GAD at 150 mg/day. Not FDA-approved due to metabolic risk-benefit concerns. Evidence quality: High.
Insomnia: Low-dose quetiapine (25–100 mg) is widely prescribed for sleep despite limited RCT data and significant metabolic risk even at low doses. Evidence quality: Low.
OCD augmentation: Modest evidence for adjunctive use with SSRIs in treatment-refractory OCD. Evidence quality: Low.
Parkinson disease psychosis: Among the atypical antipsychotics least likely to worsen motor symptoms due to low D2 affinity; some clinicians use it when clozapine monitoring is impractical, though pimavanserin is FDA-approved for this indication. Evidence quality: Low (RCTs show mixed results; AAN rates evidence as insufficient).
Dosing
Seroquel IR — Adult Indications
| Clinical Scenario | Starting Dose | Maintenance Dose | Maximum Dose | Notes |
|---|---|---|---|---|
| Schizophrenia — adults | 25 mg BID (Day 1) | 150–750 mg/day | 750 mg/day | Increase by 25–50 mg BID-TID on Days 2–3 to reach 300–400 mg by Day 4; further adjust in increments of 25–50 mg BID at ≥2-day intervals |
| Bipolar mania — adults (mono or adjunct) | 50 mg BID (100 mg Day 1) | 400–800 mg/day | 800 mg/day | Day 2: 200 mg; Day 3: 300 mg; Day 4: 400 mg; increase up to 800 mg by Day 6 in increments ≤200 mg/day |
| Bipolar depression — adults | 50 mg QHS (Day 1) | 300 mg/day | 300 mg/day | Administer once daily at bedtime; Day 1: 50 mg, Day 2: 100 mg, Day 3: 200 mg, Day 4: 300 mg Doses above 300 mg have not shown additional benefit in bipolar depression trials |
| Bipolar I maintenance — adults | Continue stabilisation dose | 400–800 mg/day (BID) | 800 mg/day | As adjunct to lithium or divalproex; generally continue the dose at which patient was stabilised |
Paediatric Indications (IR)
| Clinical Scenario | Starting Dose | Maintenance Dose | Maximum Dose | Notes |
|---|---|---|---|---|
| Schizophrenia — adolescents 13–17 years | 25 mg BID (Day 1) | 400–800 mg/day | 800 mg/day | Titrate: Day 2: 100 mg, Day 3: 200 mg, Day 4: 300 mg, Day 5: 400 mg; further adjustments ≤100 mg/day; may give TID |
| Bipolar mania — children/adolescents 10–17 years | 25 mg BID (Day 1) | 400–600 mg/day | 600 mg/day | Titrate: Day 2: 100 mg, Day 3: 200 mg, Day 4: 300 mg, Day 5: 400 mg; further adjustments ≤100 mg/day |
Special Populations
| Clinical Scenario | Starting Dose | Maintenance Dose | Maximum Dose | Notes |
|---|---|---|---|---|
| Elderly (≥65 years) | 50 mg/day | Titrate per response | Per indication | Increase in 50 mg/day increments; clearance reduced 30–50%; higher risk of orthostatic hypotension and falls |
| Hepatic impairment | 25 mg/day | Titrate per response | Per indication | Increase in 25–50 mg/day increments; quetiapine is extensively hepatically metabolised |
| With strong CYP3A4 inhibitors | Reduce quetiapine dose to 1/6th of original | E.g., ketoconazole, itraconazole, ritonavir, nefazodone; increase back 6-fold when inhibitor is stopped | ||
| With strong CYP3A4 inducers | Increase quetiapine dose up to 5-fold | E.g., phenytoin, carbamazepine, rifampin, St. John’s Wort; reduce back within 7–14 days of stopping inducer | ||
The IR formulation is given BID or TID; the XR is given once daily, typically at bedtime. Both are bioequivalent overall (similar AUC), but XR has a delayed Tmax (~5–6 h vs 1–2 h) and 13% lower Cmax, which may reduce peak-related sedation. XR should not be crushed or chewed. When switching between IR and XR, a mg-for-mg total daily dose conversion is generally appropriate. XR has the additional MDD adjunctive indication not shared by IR. Avoid heavy or fatty meals with XR as they increase Cmax by 44–52%.
Pharmacology
Mechanism of Action
Quetiapine is a dibenzothiazepine derivative that acts as an antagonist at multiple neurotransmitter receptors. Its antipsychotic efficacy is attributed to combined antagonism at serotonin 5-HT2A receptors and dopamine D2 receptors, with a notably higher affinity for 5-HT2A than D2. This receptor binding profile, characterised by rapid D2 dissociation, is thought to explain its low propensity for extrapyramidal symptoms compared to typical antipsychotics. Quetiapine also has significant affinity for histamine H1 receptors (mediating sedation and weight gain), adrenergic alpha-1 receptors (mediating orthostatic hypotension), and moderate affinity for alpha-2 and 5-HT1A receptors. Its active metabolite norquetiapine (N-desalkylquetiapine) inhibits the norepinephrine transporter (NET) and acts as a partial agonist at 5-HT1A receptors, properties thought to contribute to the antidepressant and anxiolytic effects that distinguish quetiapine from other atypical antipsychotics. Quetiapine has negligible affinity for muscarinic receptors, although norquetiapine does exhibit antimuscarinic activity, accounting for some anticholinergic-type side effects.
ADME Profile
| Parameter | Value | Clinical Implication |
|---|---|---|
| Absorption | Rapidly absorbed; Tmax ~1–2 h (IR), ~5–6 h (XR); bioavailability ~100% (tablet vs solution); food has minimal effect on IR but increases XR Cmax by 44–52% | IR can be taken with or without food; XR should be taken without food or with a light meal to avoid excessive peak concentrations |
| Distribution | Vd ~10 L/kg; 83% plasma protein binding | Extensive tissue distribution; moderate protein binding unlikely to cause clinically significant displacement interactions |
| Metabolism | Extensively hepatic via CYP3A4 (primary) and CYP2D6; active metabolite norquetiapine (N-desalkylquetiapine); 11 metabolites identified; ~73% excreted in urine, ~21% in feces as metabolites | Strong CYP3A4 inhibitors require 6-fold dose reduction; strong inducers require up to 5-fold dose increase; quetiapine does not significantly inhibit CYP enzymes; not affected by smoking |
| Elimination | t½ ~7 h (parent compound); ~12 h (norquetiapine); steady state in ~2 days; linear pharmacokinetics across clinical dose range | Short half-life necessitates BID dosing for IR; XR provides once-daily convenience; clearance reduced 30–50% in elderly |
Side Effects
Quetiapine’s side effect profile is shaped by its multi-receptor pharmacology: H1 antagonism drives sedation and weight gain, alpha-1 antagonism causes orthostatic hypotension, and metabolic effects (hyperglycaemia, dyslipidaemia) are a class-wide atypical antipsychotic concern. Data below are from pooled short-term placebo-controlled trials in the FDA PI (Rev 01/2025).
| Adverse Effect | Incidence | Clinical Note |
|---|---|---|
| Somnolence / sedation | 18–57% | Most common adverse effect across all indications; dose-related; highest with bipolar mania dosing; may diminish over time; primary reason for nocturnal dosing strategy |
| Dry mouth | 9–44% | Mediated partly by norquetiapine’s antimuscarinic activity; higher incidence with XR formulation; counsel on oral hygiene and dental care |
| Dizziness | 8–18% | Related to orthostatic hypotension via alpha-1 antagonism; most prominent during initial titration; reduce risk with slow titration |
| Weight gain (≥7% body weight) | 8–23% | Schizophrenia 23% vs 6% placebo; bipolar mania 21% vs 7%; bipolar depression 8% vs 2% (FDA PI Table 6); mean gain 2–3 kg in short-term trials; more pronounced in paediatric patients |
| Constipation | 6–11% | Anticholinergic mechanism via norquetiapine; monitor in elderly; advise adequate fluid and fibre intake |
| Increased appetite | 5–12% | H1 antagonism drives appetite stimulation; contributes to weight gain; higher in paediatric patients |
| Adverse Effect | Incidence | Clinical Note |
|---|---|---|
| Orthostatic hypotension | 4–7% | Alpha-1 blockade; syncope in 1% of Seroquel patients (vs 0.2% placebo); highest risk during initial titration and in elderly; assess fall risk |
| Tachycardia | 3–7% | Compensatory response to orthostasis; paediatric incidence higher; monitor in patients with cardiovascular disease |
| Dyspepsia / abdominal pain | 3–7% | May improve with food; may overlap with constipation-related discomfort |
| Fatigue / asthenia / lethargy | 3–10% | Distinct from somnolence; persistent fatigue may warrant dose adjustment |
| ALT increased | 1–5% | Transaminase elevations >3× ULN in ~1% of patients; usually within first 3 weeks; typically resolves with continued treatment |
| Nasal congestion / pharyngitis | 3–6% | Autonomic effect; generally mild |
| Dysarthria | 1–4% | More common with XR; dose-related; may be confused with oversedation |
| Adverse Effect | Estimated Frequency | Typical Onset | Required Action |
|---|---|---|---|
| Metabolic syndrome (hyperglycaemia, dyslipidaemia, weight gain) | Common; fasting glucose shift to ≥126 mg/dL in 2.4% (normal baseline) vs 1.4% placebo | Weeks to months | Monitor fasting glucose, HbA1c, and lipid panel at baseline, 12 weeks, then annually; total cholesterol ≥240 in 18% (schizophrenia) vs 7% placebo; triglycerides ≥200 in 22% vs 16%; manage per ADA/AHA guidelines |
| Neuroleptic malignant syndrome | Rare | Any time; higher risk at initiation or dose change | Discontinue immediately; supportive care including cooling, hydration; monitor CK, renal function; dantrolene or bromocriptine may be considered |
| Tardive dyskinesia | Low but risk increases with duration and cumulative dose | Months to years | May be irreversible; consider discontinuation if clinically appropriate; VMAT2 inhibitors (valbenazine, deutetrabenazine) are approved treatments |
| Agranulocytosis / severe neutropenia | Rare (including fatal cases reported) | First few months most common | Obtain CBC if unexplained fever or infection; discontinue if ANC <1000/mm³; monitor WBC until recovery; those with pre-existing low WBC need frequent early monitoring |
| QT prolongation | Uncommon at therapeutic doses; reported in overdose and with risk factors | Any time | Avoid in patients with congenital long QT, uncompensated heart failure, or concurrent QT-prolonging drugs; ECG if symptomatic |
| Seizures | 0.5% (20/3490) vs 0.2% placebo | Any time | Use cautiously with history of seizures or conditions lowering seizure threshold; no dose-specific threshold established |
| Cataracts | Observed in animal studies; lens changes reported in humans but causal link not established | Months to years | Slit-lamp examination at baseline and every 6 months during chronic treatment per FDA PI |
| Hypothyroidism | Dose-related; ~20% reduction in total and free T4 at higher doses; reciprocal T4/TSH shifts in 0.1% of adults | First 6 weeks, maximal effect | Monitor thyroid function at baseline and periodically; clinically overt hypothyroidism is uncommon but can occur; paediatric TSH elevation in 2.9% vs 0.7% placebo; treat with levothyroxine if warranted |
Quetiapine carries clinically significant metabolic risk across all indications and doses. In schizophrenia trials, 23% of quetiapine patients gained ≥7% body weight vs 6% on placebo, and 18% developed total cholesterol ≥240 mg/dL vs 7% on placebo (FDA PI Tables 4 and 6). Baseline metabolic screening (weight, waist circumference, fasting glucose, HbA1c, lipid panel) should be performed before initiation. Repeat metabolic labs at 12 weeks and then at least annually. Counsel patients on diet, exercise, and the importance of regular metabolic monitoring throughout treatment. If metabolic parameters worsen significantly, consider switching to a metabolically lower-risk agent.
Drug Interactions
Quetiapine is primarily metabolised by CYP3A4, making it susceptible to significant interactions with strong CYP3A4 inhibitors and inducers. Quetiapine itself does not significantly inhibit any major CYP isoforms at clinically relevant concentrations and does not affect lithium levels. Pharmacodynamic interactions involve additive CNS depression and QT prolongation risk.
Monitoring
- Weight / BMIBaseline, monthly for 3 months, then quarterly
Routine23% of schizophrenia patients gain ≥7% body weight. Paediatric weight gain should be assessed against expected growth. Consider dietary counselling and exercise guidance at initiation. - Fasting Glucose / HbA1cBaseline, 12 weeks, then annually
RoutineMonitor for new-onset diabetes; fasting glucose shift to ≥126 mg/dL in 2.4% of normal-baseline patients vs 1.4% placebo. More frequently in patients with diabetes risk factors. - Fasting Lipid PanelBaseline, 12 weeks, then annually
RoutineTotal cholesterol ≥240 mg/dL in 18% (schizophrenia) vs 7% placebo; triglycerides ≥200 mg/dL in 22% vs 16%. Manage dyslipidaemia per standard guidelines. - Blood PressureBaseline, during titration, periodically
RoutineOrthostatic BP measurements during initial titration. In paediatric patients, monitor for BP increases (systolic ≥20 mmHg in 15% vs 6% placebo; diastolic ≥10 mmHg in 41% vs 25%). - Eye ExaminationBaseline, then every 6 months
RoutineSlit-lamp exam for cataract detection per FDA PI (Section 5.11). Lens changes observed in chronic dog studies and reported in human patients. - Thyroid FunctionBaseline and periodically
RoutineQuetiapine causes dose-related ~20% reduction in total and free T4; clinically significant TSH elevation in 2.9% of paediatric patients vs 0.7% placebo. - CBCBaseline; frequent early monitoring if pre-existing low WBC
Trigger-basedAgranulocytosis reported (including fatal cases). Discontinue if ANC <1000/mm³. Monitor more frequently in patients with pre-existing leukopenia or history of drug-induced neutropenia. - Abnormal MovementsEvery visit
RoutineScreen for tardive dyskinesia using AIMS or equivalent scale. Low EPS risk relative to typical antipsychotics, but cumulative risk increases with duration.
Contraindications & Cautions
Absolute Contraindications
- Hypersensitivity — to quetiapine or any excipient; anaphylactic reactions have been reported
Relative Contraindications (Specialist Input Recommended)
- Dementia-related psychosis in elderly — boxed warning for increased mortality (1.6–1.7× vs placebo); not approved for this use
- Congenital long QT syndrome or concurrent QT-prolonging drugs — risk of torsades de pointes; ECG monitoring if co-administration is unavoidable
- Uncontrolled diabetes mellitus — quetiapine may worsen glycaemic control; close monitoring required if used
- History of NMS — careful risk-benefit assessment; may consider cautious re-challenge with different antipsychotic class
Use with Caution
- Cardiovascular disease — orthostatic hypotension and tachycardia; slow titration in patients with ischaemic heart disease, heart failure, or conduction abnormalities
- Seizure history — seizures in 0.5% of quetiapine patients vs 0.2% placebo; use cautiously with conditions lowering seizure threshold
- Hepatic impairment — reduced clearance; start at 25 mg/day and titrate slowly
- Elderly — 30–50% reduced clearance; increased fall risk from orthostasis and sedation; start at 50 mg/day
- Body temperature dysregulation — strenuous exercise, extreme heat, concurrent anticholinergics, or dehydration may impair thermoregulation
- Third trimester of pregnancy — neonatal EPS and/or withdrawal symptoms (agitation, hypertonia, tremor, feeding difficulty) reported
Elderly patients with dementia-related psychosis treated with antipsychotic drugs are at an increased risk of death (4.5% vs 2.6% placebo over 10 weeks). Most deaths were cardiovascular or infectious in nature. Quetiapine is not approved for dementia-related psychosis. Additionally, antidepressants (including quetiapine when used for bipolar depression or MDD) increase the risk of suicidal thoughts and behaviour in children, adolescents, and young adults. Monitor closely for clinical worsening and emergence of suicidality, especially during the initial months of treatment or at dose changes.
Patient Counselling
Purpose of Therapy
Quetiapine is prescribed to help manage symptoms of conditions including schizophrenia, bipolar disorder (both manic and depressive episodes), and depression. It works by affecting several chemical messenger systems in the brain to help stabilise mood, reduce psychotic symptoms, and improve sleep. The dose varies significantly depending on the condition being treated — lower doses are used for bipolar depression and much higher doses for schizophrenia and mania.
How to Take
Take quetiapine exactly as prescribed. The immediate-release form is usually taken two or three times daily; the extended-release form is taken once daily, preferably in the evening without food or with a light meal. Swallow XR tablets whole — do not crush, chew, or break them. Your prescriber will start you on a low dose and gradually increase it over several days. Do not stop taking quetiapine suddenly without medical advice, as this may cause withdrawal symptoms.
Sources
- SEROQUEL (quetiapine) tablets. Full Prescribing Information. AstraZeneca Pharmaceuticals LP. Revised 01/2025. FDA LabelPrimary regulatory source for all Seroquel IR dosing, adverse reaction data (Tables 3–7), contraindications, and warnings.
- SEROQUEL XR (quetiapine) extended-release tablets. Full Prescribing Information. Revised 2020. FDA LabelXR-specific label including MDD adjunctive indication, XR-specific adverse reaction data, and dosing modifications.
- Calabrese JR, Keck PE Jr, Macfadden W, et al. A randomized, double-blind, placebo-controlled trial of quetiapine in the treatment of bipolar I or II depression. Am J Psychiatry. 2005;162(7):1351–1360. DOIBOLDER I trial establishing quetiapine monotherapy at 300 mg/day and 600 mg/day for bipolar depression.
- Thase ME, Macfadden W, Weisler RH, et al. Efficacy of quetiapine monotherapy in bipolar I and II depression: a double-blind, placebo-controlled study (the BOLDER II study). J Clin Psychopharmacol. 2006;26(6):600–609. DOIBOLDER II replication study confirming quetiapine 300 mg efficacy for bipolar depression; 600 mg offered no additional benefit.
- Lieberman JA, Stroup TS, McEvoy JP, et al. Effectiveness of antipsychotic drugs in patients with chronic schizophrenia (CATIE). N Engl J Med. 2005;353(12):1209–1223. DOILandmark CATIE trial comparing atypical antipsychotics; quetiapine had higher discontinuation rate primarily due to lack of efficacy but lower metabolic impact than olanzapine.
- Vieta E, Suppes T, Eggens I, et al. Efficacy and safety of quetiapine in combination with lithium or divalproex for maintenance of patients with bipolar I disorder. J Affect Disord. 2008;109(3):251–263. DOIMaintenance trial supporting quetiapine as adjunctive therapy for bipolar I disorder relapse prevention.
- Yatham LN, Kennedy SH, Parikh SV, et al. Canadian Network for Mood and Anxiety Treatments (CANMAT) and International Society for Bipolar Disorders (ISBD) 2018 guidelines for the management of patients with bipolar disorder. Bipolar Disord. 2018;20(2):97–170. DOIRecommends quetiapine as first-line monotherapy for bipolar depression and as a first-line option for acute mania.
- American Psychiatric Association. Practice Guideline for the Treatment of Patients with Schizophrenia, Third Edition. Am J Psychiatry. 2021;178(supplement). DOIAPA guideline supporting atypical antipsychotic monotherapy (including quetiapine) as first-line for schizophrenia.
- Jensen NH, Rodriguiz RM, Caron MG, Wetsel WC, Rothman RB, Roth BL. N-desalkylquetiapine, a potent norepinephrine reuptake inhibitor and partial 5-HT1A agonist, as a putative mediator of quetiapine’s antidepressant activity. Neuropsychopharmacology. 2008;33(10):2303–2312. DOICharacterisation of norquetiapine’s NET inhibition and 5-HT1A partial agonism underlying quetiapine’s antidepressant mechanism.
- DeVane CL, Nemeroff CB. Clinical pharmacokinetics of quetiapine: an atypical antipsychotic. Clin Pharmacokinet. 2001;40(7):509–522. DOIComprehensive PK review covering absorption, distribution, metabolism, elimination, and effects of hepatic/renal impairment and age.
- Nemeroff CB, Kinkead B, Goldstein J. Quetiapine: preclinical studies, pharmacokinetics, drug interactions, and dosing. J Clin Psychiatry. 2002;63(Suppl 13):5–11. LinkReview of receptor binding profile, PK properties, and practical dosing considerations for quetiapine.
- Maglione M, Ruelaz Maher A, Hu J, et al. Off-label use of atypical antipsychotics: an update. Comparative Effectiveness Review No. 43. AHRQ Publication No. 11-EHC087-EF. Agency for Healthcare Research and Quality. September 2011. AHRQAHRQ systematic review of off-label atypical antipsychotic use including evidence for quetiapine in GAD, insomnia, and OCD.