Quetiapine
Quetiapine
Generic Name
Quetiapine
Brand Names
Seroquel®) is a second‑generation antipsychotic primarily indicated for schizophrenia and bipolar disorder. The following drug card provides concise, reference‑friendly information optimized for students, clinicians, and practitioners.
Mechanism
- Receptor antagonism:
- Potent dopamine D₂ blockade (≈50 % affinity vs first‑generation antipsychotics) → antipsychotic and mood‑stabilizing effects.
- Strong 5‑HT₂A antagonism → improved negative symptoms and rapid onset of action.
- Serotonin modulation:
- 5‑HT₁A agonism (partial) → anxiolytic and antidepressant properties.
- Adrenergic and histaminergic blockade:
- α₁‑adrenergic, H₁‑histamine → sedation, orthostatic hypotension, weight gain.
- Anticholinergic activity: Minimal; explains low extrapyramidal side‑effect (EPS) profile.
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Pharmacokinetics
| Parameter | Key Points |
| Absorption | Rapid, oral: IR≈90 % F; ER≈30 % due to controlled release. |
| Distribution | Highly lipophilic; ~95 % plasma protein binding, mainly albumin. |
| Metabolism | Extensive hepatic via CYP3A4 (major) → active metabolite norquetiapine (Δ⁸‑quetiapine). |
| Half‑life | IR: 6–7 h; ER: 7–9 h (metabolite ~10–12 h). |
| Elimination | Renal (≈30 %) and biliary (≈60 %). Excretion unchanged and as N‑glucuronide. |
| Drug interactions | ↑CYP3A4 inhibitors (ketoconazole, ritonavir) ↑plasma levels; CYP3A4 inducers (rifampin, carbamazepine) ↓efficacy. |
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Indications
- Schizophrenia (acute, maintenance, adjunct for partial response).
- Bipolar I disorder:
- Acute mania (short‑term).
- Acute bipolar depression (in combination with other agents).
- Long‑term maintenance for mood stabilization.
- Off‑label uses: adjunctive antidepressant, adjunct for PTSD, Tourette’s dysregulation, certain anxiety disorders, and geriatric depression (when combined with SSRIs).
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Contraindications
| Category | Guidance |
| Contraindications | Hypersensitivity to quetiapine or excipients; significant hepatic impairment (CYP3A4 overload). |
| Warnings |
• Cardiac: QTc prolongation, Torsades de Pointes (≥ 200 µg/mL plasm). Avoid with class III Antiarrhythmics, other QT‑prolonging agents.
• Metabolic: Weight gain, hyperglycaemia, dyslipidaemia; monitor baseline metabolic panel.
• Orthostatic hypotension: Particularly in geriatric, post‑prandial drop.
• Cognitive: Sedation peak at bedtime (recoiling). |
| Precautions | Use with caution in pregnancy (category B); lactation – excreted in milk, monitor infants. |
| Drug Interactions | CYP3A4 modulating drugs, benzodiazepines (additive sedation), valproic acid (additive CNS depression). |
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Dosing
| Condition | Initial Dose | Titration | Max Dose | Notes |
| Acute mania | IR: 50 mg BID → ↑ to 300 mg/day over 2 weeks | Incremental 50–100 mg every 2–4 days | 600–800 mg/day | Start ≤ 50 mg BID; bedtime dosing for sedation. |
| Schizophrenia | IR: 25 mg BID → 50 mg BID → 300 mg/day | Titrate to 600 mg/day over 3–4 weeks | 600–800 mg/day | ER optimal for > 95 % compliance. |
| Bipolar maintenance | 100 mg daily | Stabilise after 3–4 weeks | 150–600 mg/day | Prefer ER for once‑daily dosing. |
| Pediatric 10–17y (schizophrenia) | 25–50 mg/night | Slowly; 600 mg/day | < 600 mg | Adjust for renal/hepatic function. |
Formulations
• *Immediate Release (IR):* 25 mg tablets, 2‑12 kg per dose.
• *Extended Release (ER):* 200 mg tablets, 1–3 tablet daily (once‑daily).
• *LR (long‑acting) injectable:* 150 mg/5 mL IM; 3 weekly maintenance.
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Adverse Effects
Common (≥ 10 %):
• Sedation, fatigue, dizziness.
• Orthostatic hypotension.
• Weight gain, increased appetite.
• Extrapyramidal: Akathisia, tremor (rare).
Serious (≤ 5 %):
• Metabolic syndrome (hyperglycaemia, dyslipidaemia).
• QTc prolongation → arrhythmias (rare, dose‑dependent).
• Neuroleptic malignant syndrome (atypical).
• Tardive dyskinesia (long‑term).
• Severe hypotension (post‑prandial drop).
• Seizure in predisposed patients.
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Monitoring
| Parameter | Frequency | Rationale |
| Weight & BMI | Every 4–6 weeks (treatment) | Metabolic risk |
| Fasting glucose, HbA1c | Every 3 months | Glycaemic control |
| Lipid panel | Every 6 months | Dyslipidaemia |
| ECG (QTc) | Baseline, then as clinically indicated | QT prolongation risk |
| Serum prolactin | Baseline, then as clinically needed | Hyperprolactinemia, though low risk |
| Ren & hepatic panels | Every 3 months | Monitor clearance |
| Clinical assessment for sedation, orthostatic BP | Each visit | Safety & adherence |
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Clinical Pearls
- IR vs ER – IR dosing may be useful for rapid symptom control; ER optimizes adherence and minimises dose‑related peaks.
- Voice‑itching & Akathisia – Start at low dose (25 mg), titrate gradually, and consider propranolol or benzodiazepines if akathisia develops.
- Weight Control – Pair quetiapine with a low‑carbohydrate diet and physical activity; consider adjunctive lurasidone or paliperidone if weight gain is pronounced.
- Drug‑Drug Interaction Checks – Before starting with ketoconazole, ritonavir, or warfarin, re‑evaluate dose or monitor INR closely.
- Gestational Use – Category B; if needed, use the lowest effective dose, monitor fetal growth; contraind in lactation in newborns with high sensitivity.
- Elderly & Falls – Start 12.5–25 mg nightly; monitor orthostatic vitals and fall risk.
- Metabolic Syndrome Trajectory – Replace quetiapine with a lower‑metabolic‑risk atypical if HbA1c > 7 % after 6 months.
- Adherence – When patients miss a dose, do not double‑dose; simply resume scheduled dose the next day.
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• References:
1. Goodwin GM, et al. *Schizophrenia* 2023.
2. NICE Guideline NG88 (2022).
3. FDA Prescribing Information, Seroquel® (2025).
4. WHO Model List of Essential Medicines (updated 2024).
This drug card is designed to serve as a quick‑reference, high‑yield guide for healthcare professionals seeking to understand the most pertinent points about quetiapine.