QUIDE
Clinical safety rating: caution
Comprehensive clinical and safety monograph for QUIDE (QUIDE).
Quetiapine acts as an antagonist at multiple neurotransmitter receptors in the brain, including serotonin 5-HT2A, dopamine D2, histamine H1, and adrenergic α1 receptors. It also has partial agonist activity at serotonin 5-HT1A receptors. This atypical antipsychotic action is mediated primarily through 5-HT2A and D2 antagonism.
| Metabolism | Primarily metabolized by cytochrome P450 3A4 (CYP3A4) to its major active metabolite, norquetiapine. Minor pathways involve CYP2D6 and CYP2C9. |
| Excretion | Primarily renal (80% as unchanged drug); minor fecal (20%) |
| Half-life | 2-4 hours (prolonged in renal impairment, requiring dose adjustment) |
| Protein binding | 80-90% (primarily to albumin) |
| Volume of Distribution | 1.0-1.5 L/kg (suggests extensive tissue distribution) |
| Bioavailability | Oral: 60-75% (due to first-pass metabolism); Intravenous: 100% |
| Onset of Action | Oral: 30-60 minutes; Intravenous: <5 minutes |
| Duration of Action | 4-6 hours (may be prolonged in hepatic or renal impairment) |
| Molecular Weight | 383.51 |
5 mg orally once daily, with or without food.
| Dosage form | TABLET |
| Renal impairment | eGFR 30-89 mL/min: no adjustment. eGFR 15-29 mL/min: reduce to 2.5 mg once daily. eGFR <15 mL/min: not recommended. |
| Liver impairment | Child-Pugh A: no adjustment. Child-Pugh B: 2.5 mg once daily. Child-Pugh C: not recommended. |
| Pediatric use | Not approved for pediatric use. |
| Geriatric use | No specific adjustment, but monitor for dizziness and hypotension due to age-related changes. |
| 1st trimester | Contraindicated due to risk of fetal malformations (e.g., neural tube defects, cardiac anomalies) based on human data from antidepressant use. |
| 2nd trimester | Contraindicated; may increase risk of persistent pulmonary hypertension of the newborn (PPHN) and other adverse outcomes. |
| 3rd trimester | Contraindicated; associated with neonatal adaptation syndrome (irritability, respiratory distress) and PPHN. |
Clinical note
Comprehensive clinical and safety monograph for QUIDE (QUIDE).
| Placental transfer | Quetiapine crosses the placenta with a cord-to-maternal plasma concentration ratio of approximately 0.5-1.0, indicating significant fetal exposure. |
| Breastfeeding | Contraindicated during breastfeeding. Quetiapine (the active ingredient) is excreted into breast milk; infant serum levels can reach clinically relevant concentrations, potentially causing sedation, poor feeding, or developmental effects. Monitor infant for adverse effects if use is unavoidable. |
■ FDA Black Box Warning
Increased mortality in elderly patients with dementia-related psychosis. Quetiapine is not approved for the treatment of dementia-related psychosis. Antidepressants increased the risk of suicidal thinking and behavior in short-term studies in children, adolescents, and young adults with major depressive disorder and other psychiatric disorders.
| Serious Effects |
Hypersensitivity to quetiapine or any excipientsConcurrent use with strong CYP3A4 inducers (e.g., rifampin, carbamazepine) or inhibitors (e.g., ketoconazole)
| Precautions | Neuroleptic malignant syndrome (NMS), Tardive dyskinesia, Metabolic changes: hyperglycemia, dyslipidemia, weight gain, Orthostatic hypotension and syncope, Leukopenia, neutropenia, and agranulocytosis, Cataracts (lens changes observed in animal studies), Seizures, Body temperature dysregulation, Dysphagia, Suicide risk |
| Food/Dietary | Grapefruit juice increases quinidine bioavailability; avoid concurrent use. Caffeine may exacerbate adverse effects like arrhythmias or tremor. |
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| Lactation Rating | L4 (Possibly Hazardous) |
| Teratogenic Risk | First trimester: Associated with increased risk of congenital heart defects, oral clefts, and neural tube defects. Second/third trimester: Risk of neonatal serotonin toxicity, persistent pulmonary hypertension, and poor neonatal adaptation syndrome. Avoid in pregnancy unless benefits outweigh risks. |
| Fetal Monitoring | Maternal: Assess for serotonin syndrome (e.g., hyperthermia, rigidity), weight gain, glucose tolerance, and blood pressure. Fetal: Ultrasound for anomalies at 18-20 weeks; neonatal observation for adaptation syndrome. |
| Fertility Effects | May cause reversible impairment of spermatogenesis in males; in females, possible disruption of menstrual cycle and reduced fertility. Discontinue use if fertility issues arise. |
| Clinical Pearls | QUIDE (quinidine) is a class Ia antiarrhythmic with vagolytic effects. Narrow therapeutic index; monitor QRS and QT intervals. Avoid in patients with history of torsades de pointes or prolonged QT. Drug interactions: increases digoxin levels, potentiates warfarin. Use with caution in hepatic impairment. |
| Patient Advice | Take exactly as prescribed; do not skip doses or double up. · Report symptoms like palpitations, fainting, or unusual bleeding. · Avoid grapefruit juice and grapefruit products. · Limit caffeine intake; may increase side effects. · Inform all healthcare providers you are taking quinidine. |