clozapine at a glance
Medicine class
Atypical antipsychotic
Usual role
Treatment-resistant schizophrenia; selected cases of psychosis in Parkinson’s disease
Essential monitoring
Regular blood counts through a brand-linked clozapine monitoring service
Food
May be taken with or without food
Important practical point
Smoking changes, infection and missed treatment require prompt specialist review
What is clozapine used for?
Licensed uses represented by the selected products include:
Treatment-resistant schizophrenia, including when other antipsychotics have caused severe neurological adverse effects that cannot be treated.
Psychotic disorders occurring during Parkinson’s disease when standard treatment has failed.
How does clozapine work?
Clozapine changes signalling at several brain receptors. Its effects on dopamine, serotonin, histamine, muscarinic and alpha-adrenergic receptors contribute to both its antipsychotic action and effects such as sedation, dizziness, saliva changes and constipation.
clozapine preparations and strengths
Oral suspension
Route: Oral
Strengths: 50 mg/mL
Tablet
Route: Oral
Strengths: 25 mg, 50 mg, 100 mg, 200 mg
How to take clozapine
Take clozapine exactly as directed and do not change or stop it without specialist advice. It may be taken with or without food.
Remove an orodispersible tablet with dry hands, place it on the tongue and allow it to disperse in saliva; liquid is optional.
Shake Denzapine oral suspension before use and measure it with the supplied oral dispenser.
The suspension may be swallowed directly or mixed with water, but not fruit juice or another liquid.
Tell the team promptly if swallowing or supply problems could interrupt treatment.
clozapine side effects
Common or expected effects
- Drowsiness or sedation
- Dizziness
- Fast heartbeat
- Constipation
- Excess saliva or drooling
- Nausea or vomiting
- Dry mouth
- Weight gain
- A fall in blood pressure on standing
Get urgent medical advice
- Fever, sore throat, flu-like illness or infection suggesting neutropenia or agranulocytosis
- Persistent fast heartbeat, chest pain, breathlessness, palpitations or unexplained severe fatigue suggesting myocarditis or cardiomyopathy
- Severe constipation, abdominal swelling, pain or vomiting suggesting bowel obstruction
- Seizure, collapse or profound sedation
- High temperature with marked muscle stiffness, sweating or altered consciousness
- Jaundice or other symptoms of significant liver injury
- A widespread rash with fever, facial swelling or organ symptoms
clozapine in pregnancy
Clozapine can be used during pregnancy when recommended by a specialist, but experience is limited. Exposure near delivery can cause temporary newborn feeding, sleeping, movement or breathing problems. Do not stop clozapine suddenly after discovering a pregnancy; specialist maternity and mental-health planning is important.
clozapine while breastfeeding
Specialist advice is essential before breastfeeding. Evidence is limited, and product information advises against breastfeeding because clozapine may enter breast milk and potentially cause serious infant effects.
clozapine interactions
Clozapine has important metabolic and additive interactions. Check prescribed, over-the-counter and herbal products with the clozapine team.
Carbamazepine and other substantial bone-marrow suppressants
Can increase bone-marrow suppression and should not be combined with clozapine where contraindicated by product information.
Ciprofloxacin, fluvoxamine and other strong CYP1A2 inhibitors
Can markedly increase clozapine exposure and toxicity.
Rifampicin, phenytoin and other enzyme inducers
Can lower clozapine concentrations and reduce effectiveness; stopping an inducer can reverse this effect.
Common questions about clozapine
Answers are fully visible for fast scanning and source review.
Why does clozapine require regular blood tests?
It can cause neutropenia or agranulocytosis, reducing white blood cells needed to fight infection. Monitoring helps detect this early.
Does smoking affect clozapine?
Yes. Tobacco smoke speeds up clozapine metabolism, while stopping or reducing smoking can raise concentrations and toxicity. Tell the specialist team promptly about changes; nicotine replacement and vaping do not reproduce tobacco smoke’s effect.
Sources
These sources were used to prepare and review this medicine page.
Prepared and reviewed by the iatroX editorial team.