Drug reference

Quetiapine

Atypical Antipsychotic · Antipsychotic

Also known as Quetiapine Fumarate, Seroquel, Seroquel XR, Q-Pin, Qutipin

START

Confirm indication. Baseline weight, BMI, fasting glucose, lipid panel, ECG (QTc). Start low (25-50 mg BID) and titrate gradually over 4-5 days to minimize orthostatic hypotension and sedation.

TYPICAL MAX

800 mg/day (adults); 400 mg/day (elderly). XR: 300-800 mg once daily.

STOP IF

NMS, severe TD, QTc >500 ms, agranulocytosis, DKA, severe hepatotoxicity, pregnancy

WATCH

Weight/glucose/lipids (baseline, 12 weeks, then annually), ECG (QTc), EPS (AIMS), orthostatic BP, cataracts (eye exam at baseline and periodically)

CDSCO approvedSchedule HATC N05AH04

Dose laddermg/d

Renal dose adjustmenteGFR mL/min/1.73m²

KDIGO 2024 + manufacturer label

Pharmacokineticsplasma · t hours

ONSET: 23min · absorption onset
PEAK: 1.5h · 1.5 h (IR); 6 h (XR)
t½: 6h · ~6 h (parent); 7-12 h (norquetiapine)
DURATION: 12h · 8-12 h (IR BID); 24 h (XR)

EXCRETION

~73% urine (metabolites); hepatic CYP3A4 primary; CYP2D6 secondary

route + CYP

INTERACTIONS

12 major

SEVERE in our sources

PREGNANCY

FDA PLLR: Limited human data. Neonatal EPS and withdrawal symptoms reported with third-trimester exposure. Use only if benefit clearly outweighs risk. Risk of metabolic complications in pregnancy.

FDA category + note

Top interactionssee all 12 →

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Available in India

361 branded formulations. Look up specific brands in the Drugs workspace.

Mechanism

Quetiapine is a dibenzothiazepine atypical antipsychotic with a broad receptor binding profile. It has high affinity for histamine H1 receptors (potent sedation), moderate affinity for 5-HT2A and 5-HT1A receptors, and moderate affinity for dopamine D2 receptors (rapid dissociation from D2 — 'hit-and-run' kinetics). Its relatively low D2 occupancy compared to other antipsychotics accounts for its low extrapyramidal symptom risk. It also blocks alpha-1 adrenergic receptors (orthostatic hypotension) and has minimal anticholinergic activity. The active metabolite norquetiapine has higher affinity for norepinephrine reuptake transporters (NET), contributing to antidepressant effects.

Indications

Schizophrenia — acute and maintenanceBipolar I disorder — acute manic episodesBipolar depressionBipolar maintenance (as adjunct to lithium or divalproex)Major depressive disorder — adjunctive therapyGeneralized anxiety disorder (off-label)Insomnia (low-dose, off-label)Delirium (off-label)Parkinson disease psychosis (off-label — lowest EPS risk)

Dosing

Adult: Schizophrenia: Day 1: 25 mg BID; Day 2: 50 mg BID; Day 3: 100 mg BID; Day 4: 150 mg BID; titrate to 300-400 mg BID (600-800 mg/day); max 800 mg/day. Bipolar mania: 100 mg Day 1, 200 mg Day 2, 300 mg Day 3, 400 mg Day 4; target 400-800 mg/day. Bipolar depression: 50 mg Day 1, 100 mg Day 2, 200 mg Day 3; target 300 mg/day. MDD adjunct: 150-300 mg/day. Elderly: start 25 mg/day; titrate slowly; max 400 mg/day.
Pediatric: Schizophrenia (13-17 years): Day 1: 25 mg BID; titrate to 400-800 mg/day. Bipolar mania (10-17 years): Day 1: 25 mg BID; titrate to 400-600 mg/day.
Renal adjustment: Start 25 mg/day; titrate slowly. No specific adjustment but reduced clearance expected.
Hepatic adjustment: Start 25 mg/day; titrate slowly. Extensive hepatic metabolism means increased levels in hepatic impairment.
Geriatric: Start 25 mg/day; max 400 mg/day. Increased risk of sedation, orthostatic hypotension, falls, cognitive impairment, mortality in dementia.
Max dose: 800 mg/day (adults); 400 mg/day (elderly)

Pharmacokinetics

Onset

Sedation within hours. Antipsychotic effect: 1-2 weeks.

Peak effect

Oral IR: peak at 1.5 hours. XR: 6 hours. Steady-state: 2 days.

Duration

IR: 8-12 hours (BID dosing). XR: 24 hours (once daily).

Half-life

~6 hours (parent); 7-12 hours (active metabolite norquetiapine). Combined effective half-life: ~6-7 hours.

Bioavailability

Poor: ~9% (oral; extensive first-pass metabolism via CYP3A4).

Protein binding

~83% (bound to albumin and alpha-1-acid glycoprotein).

Metabolism

Extensive hepatic via CYP3A4 (primary — sulfoxidation, oxidation) and CYP2D6 (secondary — N-dealkylation to norquetiapine — active metabolite with NET inhibition). Norquetiapine contributes to antidepressant and antipsychotic effects.

Excretion

Urine: ~73% (as metabolites, <1% unchanged). Fecal: ~20%.

Contraindications

Hypersensitivity to quetiapine
Dementia-related psychosis (FDA black box warning — increased mortality)
Concomitant use with strong CYP3A4 inhibitors (may increase levels significantly)
Concomitant use with strong CYP3A4 inducers (may reduce efficacy)

Side effects

Common

Sedation, somnolence (H1 antagonism — most common, dose-related)Dizziness, orthostatic hypotension (alpha-1 blockade)Dry mouthConstipationDyspepsiaWeight gain (metabolic effects)Dyslipidemia (elevated triglycerides, cholesterol)HeadacheTachycardia

Serious

QT prolongation (dose-related; risk increased >800 mg/day)
Neuroleptic malignant syndrome (NMS)
Tardive dyskinesia (TD)
Diabetic ketoacidosis, hyperosmolar coma (rare)
Severe neutropenia, agranulocytosis
Cataracts (lens changes observed in animal studies; monitor)
Hepatotoxicity (elevated transaminases, hepatitis)
Seizures (dose-dependent lowering of threshold)
Increased mortality in dementia-related psychosis (black box warning)
Suicidal ideation (in MDD patients <24 years)

Pregnancy & lactation

Pregnancy

FDA PLLR: Limited human data. Neonatal EPS and withdrawal symptoms reported with third-trimester exposure. Use only if benefit clearly outweighs risk. Risk of metabolic complications in pregnancy.

Lactation

Excreted in breast milk. May cause infant sedation, poor feeding, developmental effects. Avoid breastfeeding if possible.