🩺 NHS Description
Clozapine (also know as Clozaril, Zaponex and Denzapine) is the most effective antipsychotic for treatment resistant schizophrenia. If you have been prescribed clozapine, your care team can provide you with detailed factsheets and leaflets. These will give information on side effects, blood tests and advice for carers when supporting someone who is taking clozapine.
🩺 Main Uses
Treatment-resistant schizophrenia, sometimes used off-label for severe aggression or suicidality.
🧪 The Science & Facts
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Half‑life (t½)
12 h
How long the drug hangs around. Longer half‑life = slower changes.
Time to Peak (Tmax)
2.5 h
Roughly when you feel the main effect after a dose.
What it hits (receptors)
Primary:
Secondary:
Very broad, explains sedation, hypotension, anticholinergic effects
How your body processes it (metabolism)
Smoking induces 1A2 → up to ~50% lower levels; stopping can raise levels by 50–72% • Always consider smoking status changes; use level monitoring per service protocol
⚠️ Warnings
- Risk of agranulocytosis — requires regular blood monitoring (weekly, then tapering).
- High sedation, weight gain, diabetes risk, metabolic syndrome.
- Seizure risk at higher doses.
- Dangerous if stopped suddenly — rebound psychosis and cholinergic rebound.
- Myocarditis/cardiomyopathy rare but serious.
⏬ Taper & Withdrawal
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If you’re reducing
Never stop abruptly unless life‑threatening reaction. For elective taper: think in months, not weeks. Example: reduce 5–10% of current dose every 2–4 weeks; go slower <200 mg/day. Watch for cholinergic rebound; prescriber may use a temporary anticholinergic (e.g., benztropine) if severe. Rebound psychosis/catatonia can occur after rapid stops.
Possible withdrawal
Cholinergic rebound (nausea, vomiting, diarrhoea, sweating), insomnia, agitation, delirium; rare but serious: catatonia, rebound psychosis. Onset often within days of abrupt cessation.
Info here is educational, not medical advice. Always taper with prescriber support if possible.
🧠 Trusted External Sources Last reviewed 22 Aug 2025, 21:19 by Connor O’Driscoll
🔗 Interaction Checker
Always verify drug interactions using the Drugs.com Checker.
Need Help Getting Off This?
Try your GP first. If that doesn't help, find local support services who understand tapering.
Find Support Near You →⚠️ Black Box Warning
⚠ Severe neutropenia (mandatory blood monitoring); ⚠ Orthostatic hypotension, bradycardia, syncope (risk highest on initiation/titration); ⚠ Seizures (dose-related); ⚠ Myocarditis and cardiomyopathy; ⚠ Increased mortality in elderly patients with dementia-related psychosis.
This is a plain‑English summary of headline safety warnings. Talk to a clinician before changing any medication.