Atypical antipsychotic – dibenzodiazepine
ATC code: N05AH02 (Clozapine)
An antagonist at dopamine D1, D2, D4, serotonin 5-HT2A, 5-HT2C, 5-HT3, muscarinic, histamine H1, and α1-adrenoceptors. The unique profile with predominant D4 affinity and low D2 affinity explains minimal extrapyramidal effects. Effective in 30–60% of treatment-resistant schizophrenia previously unresponsive to other antipsychotics. Also reduces suicide risk in schizophrenia (InterSePT 2003). CYP1A2-metabolized; smoking halves the concentration.
First line
Drug of choice for treatment-resistant schizophrenia per NG181 (2014, 2024 update) and the Spanish SEP 2024. Used after failure of at least two sequential antipsychotic trials from different classes at adequate doses. Starting dose 12.5 mg at bedtime with slow titration to 300–450 mg daily in 2–3 doses. Works in 30–60% of resistant cases – the highest rate among antipsychotics. Also indicated for suicidal behavior in schizophrenia.
The drug is promoted for these uses outside international guidelines. Each entry below is analyzed against AEMPS, FDA, EMA, Cochrane and major RCTs.
Not recommended
Clozapine is a last-line antipsychotic, not a sleep medication. It is prescribed only for treatment-resistant schizophrenia and for reducing suicide risk in schizophrenia or schizoaffective disorder ( 2020 guidelines). For insomnia, clozapine is not used: the risks far outweigh any sedative benefit. The drug can cause agranulocytosis (a sudden drop in neutrophils), myocarditis, cardiomyopathy, metabolic syndrome, orthostatic hypotension, and severe anticholinergic effects. Because of the agranulocytosis risk, the requires mandatory blood-count monitoring under the REMS program. If clozapine was prescribed for insomnia, consider seeking a second opinion immediately – this prescription is dangerous.
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Boxed warning
FDA five boxed warnings: severe neutropenia with fatal infection risk; orthostatic hypotension and syncope during titration; seizures at high doses; myocarditis and cardiomyopathy; increased mortality in older adults with dementia. Used only within a mandatory blood-monitoring program.
FDA category B. Use in pregnancy with clear indications and careful monitoring. T3 use carries neonatal extrapyramidal and withdrawal risk.
Milk concentrations are high; infant sedation and agranulocytosis are possible. Not used during lactation.
Reference information, not a clinical decision. Discuss feeding pauses or changes with your physician or an IBCLC.
Clozapine is evaluated for the following indications with varying evidence strength: Treatment-resistant schizophrenia (evidence tier A), Insomnia and sleep disorders (evidence tier F). See the full indication matrix with dosing and citations above on this page.
Common side effects of Clozapine (≥ 1 in 100): Hypersalivation (especially nocturnal), Drowsiness and sedation, Weight gain (often over 10 kg), Tachycardia, Constipation (paralytic ileus risk), Orthostatic hypotension. See the Safety section for uncommon and serious reactions.
FDA category B. FDA category B. Use in pregnancy with clear indications and careful monitoring. T3 use carries neonatal extrapyramidal and withdrawal risk.
Milk concentrations are high; infant sedation and agranulocytosis are possible. Not used during lactation.
Clozapine is contraindicated in: Clozapine hypersensitivity; History of agranulocytosis or severe neutropenia on clozapine; Bone marrow suppression; Active myeloproliferative disease, myelodysplastic syndromes; Paralytic ileus. Full list in the Safety section.
FDA five boxed warnings: severe neutropenia with fatal infection risk; orthostatic hypotension and syncope during titration; seizures at high doses; myocarditis and cardiomyopathy; increased mortality in older adults with dementia. Used only within a mandatory blood-monitoring program.