Clinical safety rating: caution
Animal studies have demonstrated safety
Antagonist at serotonin 5-HT2A, dopamine D2, histamine H1, and adrenergic α1 receptors; weak partial agonist at 5-HT1A and serotonin transporter.
| Metabolism | Hepatic via CYP3A4 (major), CYP2D6 (minor); active metabolite norquetiapine via N-dealkylation. |
| Excretion | Renal: 73% (as metabolites), Fecal: 20% (as metabolites), unchanged drug: <1% renal |
| Half-life | Terminal elimination half-life: ~6-7 hours (parent drug); extended-release: ~7 hours. Clinically, dosing is twice daily for immediate-release; once daily for extended-release. |
| Protein binding | 83% bound to serum proteins (primarily albumin). |
| Volume of Distribution | 10 ± 4 L/kg (large Vd indicating extensive tissue distribution). |
| Bioavailability | Oral immediate-release: 100% (completely absorbed with first-pass effect minimal); oral extended-release: 100% relative to immediate-release. |
| Onset of Action | Oral immediate-release: 1-2 hours for sedation; antipsychotic effect: days to weeks. Oral extended-release: 2-3 hours for sedation. |
| Duration of Action | Immediate-release: 6-8 hours for sedation; extended-release: 24 hours. Clinical effect for psychosis: continuous with regular dosing. |
| Molecular Weight | 383.51 |
| Action Class | Atypical Antipsychotic |
Initial: 25 mg PO BID, titrate to effective range 150-750 mg/day divided BID-TID; schizophrenia: 150-750 mg/day, bipolar disorder: 400-800 mg/day, major depressive disorder (adjunct): 150-300 mg/day at bedtime.
| Renal impairment | Creatinine clearance <30 mL/min: reduce dose by 25-50% based on tolerability; no specific recommendation for mild-moderate impairment. |
| Liver impairment | Child-Pugh Class A or B: initial dose 25 mg/day, increase in increments of 25-50 mg/day; Child-Pugh Class C: not recommended or use with extreme caution. |
| Pediatric use | Adolescents (13-17 y) with schizophrenia: initial 25 mg BID, target 400-800 mg/day; children (10-17 y) with bipolar mania: initial 25 mg BID, target 400-600 mg/day. Weight-based: 1.5-3 mg/kg/day in divided doses for acute mania; monitor for metabolic effects. |
| Geriatric use | Initial 25 mg/day, titrate slowly by 25-50 mg/day to minimum effective dose; increased risk of hypotension, sedation, QT prolongation; avoid doses >200 mg/day unless necessary. |
| 1st trimester | Limited human data; animal studies show no teratogenicity at clinically relevant doses. Use only if potential benefit justifies risk. |
| 2nd trimester | Limited human data; no specific malformations reported. May cause maternal metabolic effects (weight gain, hyperglycemia) that could affect pregnancy outcomes. |
| 3rd trimester | Neonatal withdrawal and extrapyramidal symptoms reported after third trimester exposure. Monitor neonate for agitation, hypertonia, hypotonia, tremors, somnolence, respiratory distress, and feeding disorder. |
Clinical note
Atypical antipsychotic used for schizophrenia, bipolar disorder, and as an adjunct in treatment-resistant depression. Registry data and cohort studies involving thousands of first-trimester exposures do not demonstrate a consistent pattern of major congenital malformations. However, neonates exposed near delivery can develop extrapyramidal symptoms and neonatal withdrawal syndrome. Associated with gestational diabetes due to metabolic effects. Untreated psychosis or bipolar disorder in pregnancy carries serious maternal and fetal risks.
| Placental transfer | Crosses placenta; fetal serum concentrations approximately 25-50% of maternal levels. Significant placental transfer documented. |
■ FDA Black Box Warning
Increased mortality in elderly patients with dementia-related psychosis; increased risk of suicidal thinking and behavior in children, adolescents, and young adults with major depressive disorder and other psychiatric disorders.
| Common Effects | Somnolence, Dizziness, Dry mouth, Constipation, Dyspepsia, Increased appetite, Weight gain, Fatigue, Headache, Asthenia, Orthostatic hypotension, Tachycardia, Nasal congestion, Elevated serum triglycerides and cholesterol |
| Serious Effects | Tardive dyskinesia, Neuroleptic malignant syndrome, Increased mortality in elderly patients with dementia-related psychosis, Suicidal thoughts or behaviors (especially in young adults), Hyperglycemia and diabetes mellitus, Dyslipidemia, Weight gain, Leukopenia, neutropenia, and agranulocytosis, QT prolongation, Seizures, Orthostatic hypotension, Cataracts (associated with lenticular changes) |
Hypersensitivity to quetiapine or any excipientsConcomitant use with CYP3A4 strong inhibitors (e.g., ketoconazole, ritonavir) or strong inducers (e.g., carbamazepine, rifampin) unless benefit outweighs risk and monitoring is enhanced
| Precautions |
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| Breastfeeding | Present in breast milk in low amounts; relative infant dose estimated 0.09-1.0% of maternal weight-adjusted dose. Limited data suggests no adverse effects in breastfed infants. Monitor for sedation, poor feeding, and weight gain. Use with caution, especially in neonates and preterm infants. |
| Lactation Rating | L2 (Limited data: probably compatible) |
| Teratogenic Risk | Quetiapine is pregnancy category C. First trimester: Limited data; may increase risk of congenital malformations, particularly cardiac defects (OR 1.3-1.6). Second/third trimester: Risk of neonatal withdrawal syndrome (irritability, respiratory distress, feeding difficulties) and extrapyramidal symptoms. No clear association with neural tube defects or orofacial clefts. |
| Fetal Monitoring | Maternal: Blood glucose (risk of hyperglycemia), weight gain, blood pressure (especially if preeclampsia). Fetal: Serial growth ultrasound for macrosomia or small-for-gestational age; neonatal observation for withdrawal symptoms (7-10 days postpartum). Monitor for extrapyramidal symptoms in neonate. |
| Fertility Effects | Quetiapine may cause hyperprolactinemia leading to menstrual irregularities, galactorrhea, and sexual dysfunction, potentially impairing fertility. However, atypical antipsychotics are less likely than typical agents to elevate prolactin. In men, may reduce libido and cause erectile dysfunction. Discontinuation may restore fertility. |
| Increased mortality in elderly patients with dementia-related psychosis, Suicidality in children, adolescents, and young adults, Neuroleptic malignant syndrome, Tardive dyskinesia, Hyperglycemia/diabetes mellitus, Dyslipidemia, Weight gain, Orthostatic hypotension, Seizures, Cataracts, Leukopenia/neutropenia, Priapism, QT prolongation (rare), Body temperature dysregulation, Dysphagia, Withdrawal symptoms |
| Food/Dietary | Grapefruit and grapefruit juice may increase quetiapine levels; avoid excessive consumption. High-fat meals can increase absorption of ER formulation; take consistently with or without food. Alcohol potentiates CNS depression and sedation. |
| Clinical Pearls | Quetiapine is associated with dose-dependent sedation and orthostatic hypotension; titrate slowly. Monitor for metabolic syndrome (weight gain, dyslipidemia, hyperglycemia). QTc prolongation risk is lower than with other atypicals but caution in elderly. Short-acting IR has more sedative effect; ER form allows once-daily dosing. Avoid abrupt discontinuation to prevent withdrawal symptoms. |
| Patient Advice | Take exactly as prescribed, usually with or without food. · Avoid alcohol and CNS depressants due to additive sedation. · Do not stop suddenly; taper under medical supervision. · Report rapid heartbeat, fainting, or unusual thoughts/behavior. · May cause drowsiness, especially when starting; avoid driving until you know how it affects you. · Weight gain and increased appetite are common; monitor weight and blood sugar regularly. |