Clozaril (Clozapine)
Also sold as: Clozaril, Sizopin, Lozapin, Clopin, Fazaclo
Pregnancy
Cat B
Lactation
Avoid
Schedule
H
Forms
Tablet 25mg, 100mg, 200mg +1
Indications
- Treatment-resistant schizophrenia (defined as failure of 2 adequate antipsychotic trials — clozapine is the gold standard)
- Suicidality in schizophrenia/schizoaffective disorder (FDA-approved indication)
- Parkinson's disease psychosis (low-dose — only atypical without worsening motor function)
- Persistent aggressive behaviour in schizophrenia
Adult Dosing
Treatment-resistant schizophrenia
Start 12.5 mg PO OD or BD Day 1; increase by 25–50 mg/day over 2–3 weeks to target 300–450 mg/day in divided doses
Slow titration essential (hypotension, seizures at higher doses). Target serum level 350–600 ng/mL (therapeutic drug monitoring recommended). Maximum 900 mg/day.
Pediatric Dosing
Paediatric safety data limited; specialist child psychiatrist must supervise
Renal Dose Adjustment
| CrCl / eGFR | Dose Adjustment |
|---|---|
| Significant CKD | Use with caution — no specific dose adjustment but risk of metabolite accumulation |
Hepatic Adjustment
Reduce dose in hepatic impairment; avoid in severe hepatic disease — risk of hepatic failure
Pregnancy & Lactation
Pregnancy: Category B
Continue if needed (treatment-resistant schizophrenia risk is high in pregnancy). Neonatal complications: hypotonia, seizures, respiratory depression. Use lowest effective dose; monitor neonate.
Lactation: Avoid
High concentrations in breast milk — neonatal sedation, agranulocytosis risk; avoid breastfeeding.
Top Drug Interactions
| Interacting Drug | Effect | Severity |
|---|---|---|
| Carbamazepine | ABSOLUTELY CONTRAINDICATED — both cause agranulocytosis; additive bone marrow suppression; carbamazepine also dramatically lowers clozapine levels | Major |
| SSRIs/SNRIs (fluoxetine, fluvoxamine, ciprofloxacin) | CYP1A2 inhibition — increase clozapine levels 2–5× — reduce clozapine dose; fluvoxamine is the most potent inhibitor (avoid) | Major |
| Smoking (tobacco — CYP1A2 inducer) | Smoking dramatically REDUCES clozapine levels. If patient stops smoking, clozapine levels may double — toxicity risk. If patient starts/resumes smoking, levels fall. | Major |
| Benzodiazepines (concurrent IV) | Respiratory arrest and cardiac collapse reported with concurrent IV diazepam + clozapine — avoid IV benzodiazepines; oral with caution | Major |
| Rifampicin | Reduces clozapine levels by 75% — avoid | Major |
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Side Effects
Common
- Hypersalivation (sialorrhoea — excessive drooling — most characteristic side effect; especially at night)
- Sedation (significant)
- Weight gain and metabolic syndrome (obesity, diabetes, hyperlipidaemia)
- Constipation (severe — potentially fatal ileus)
- Orthostatic hypotension
- Tachycardia
- Seizures (dose-related, > 600 mg/day risk)
- Hyperthermia (benign — common in first weeks)
Serious / Discontinue If
- Agranulocytosis (1% — potentially fatal; MANDATORY WBC/ANC monitoring)
- Myocarditis and cardiomyopathy (rare, fatal — especially in first 4–8 weeks; monitor CRP, troponin, ECG)
- Fatal constipation/ileus (severely underestimated — proactive bowel monitoring essential)
- Pulmonary embolism (increased risk)
- Seizures (grand mal)
Contraindications
- History of clozapine-induced agranulocytosis
- Concurrent carbamazepine
- Severe hepatic impairment
- Uncontrolled epilepsy
- Severe cardiac disease (myocarditis, cardiomyopathy)
- Bone marrow depression (any cause)
- Unable to comply with WBC monitoring programme
Available Indian Brands
| Brand | Manufacturer | Price (approx) |
|---|---|---|
| Sizopin 100mg | Sun Pharma | 30 tab ₹185 |
| Lozapin 100mg | Intas | 30 tab ₹175 |
| Clopin 100mg | Cipla | 30 tab ₹165 |
| Clozaril 100mg | Novartis | 30 tab ₹375 |
Monitoring Required
- WBC + ANC (absolute neutrophil count) — MANDATORY: weekly × 18 weeks, then fortnightly × 1 year, then monthly. STOP if ANC < 1.5 × 10⁹/L; STOP IMMEDIATELY if ANC < 1.0 × 10⁹/L (agranulocytosis)
- CRP and troponin (weekly × 4 weeks — myocarditis)
- Fasting glucose and HbA1c (metabolic syndrome)
- Lipids annually
- Weight and BMI monthly
- ECG (baseline; repeat if symptoms)
- Bowel movements diary (constipation — treat prophylactically)
- Clozapine serum levels (TDM: target 350–600 ng/mL)
Patient Counseling Points
- ⚠️ Blood tests EVERY WEEK for 18 weeks then every 2 weeks — this is MANDATORY and not optional. Clozapine will not be dispensed without blood test results.
- Drooling during sleep is very common — sleep on your side; atropine eyedrops under the tongue can help
- Constipation is a SERIOUS concern — take laxatives regularly as prescribed; drink plenty of water; tell your doctor if you haven't had a bowel movement in 2 days
- ⚠️ If you smoke or plan to STOP smoking — tell your doctor immediately; your dose will need adjustment
- If you develop fever, sore throat, mouth ulcers — go to emergency immediately with your blood test record
- Get weighed every month — weight gain is common and can be managed with diet/activity
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Clinically reviewed by: Dr. Vikas Desai, MD (Psychiatry), Senior Consultant Psychiatrist
Last reviewed: 2026-04-01
References
- NICE Schizophrenia Guidelines 2014 (updated 2019)
- RANZCP Clozapine Monitoring Guidelines
- BNF — Clozapine
- Lancet — Clozapine and Suicidality
- ICMR Treatment-Resistant Schizophrenia Guidelines