Clozapine

For an informed discussion with your doctor or pharmacist. This information collection is not a clinically validated interaction checker. Missing data do not establish safety. Do not change or stop prescribed medicines on the basis of this information. The findings apply to the specific conditions studied; laboratory and animal studies cannot be directly extrapolated to humans.

Active substance: Clozapine

Examples of brand names: Leponex [DE]

ATC code: N05AH02

Main use (for orientation): Schizophrenia

Documented research summary

A case report describes an increase in clozapine concentrations/confusion after cessation of concurrent tobacco and cannabis smoking. Smoke-induced enzyme induction must be distinguished from THC/CBD; the cannabis contribution cannot be isolated. Cancloz 2024 is a study protocol, not an efficacy or interaction result. In mice, THC did not alter the neurobehavioural effects of clozapine; this does not establish clinical safety.

Uncertainties and limitations

Tobacco and cannabis are confounded in the smoking-cessation case. No reliable isolated CBD/THC–clozapine pharmacokinetic effect size was found.

Separately recorded findings

1 separately recorded finding. Each statement applies to its documented study context.

Cannabis/tobacco smoke (not an isolated cannabinoid) – clinical signals

Finding ID: B0091

Type of result: Context-specific finding; read the limitations

Observation: Increased clozapine concentrations and confusion described.

Mechanism: Loss of smoke-induced CYP1A2 induction after smoking cessation

Study type: Two case reports; smoking/tobacco context

Context studied: Concurrent cessation of tobacco and cannabis smoking.

Clinical interpretation: Individual medical / pharmaceutical assessment; do not use as dosage instructions

Limitations and uncertainties: Do not attribute established causality to CBD, THC or nicotine. Separate exposure context.

Original sources for this finding: Tobacco and cannabis smoking cessation can lead to intoxication with clozapine or olanzapine [EX04]

References and access status

[CA_L_D0118] CLOZARIL (CLOZAPINE) TABLET [HLS THERAPEUTICS (USA), INC.]

Original source / bibliographic reference

Authors: HLS Therapeutics (USA), Inc.

Year: 2025

Source type: Current published human-use SPL / product information

Source access – 23 October 2026: Source destination was accessible when checked.

Bibliographic attribution or source identity cross-checked.

[EX04] Tobacco and cannabis smoking cessation can lead to intoxication with clozapine or olanzapine

Original source / bibliographic reference

Authors: Zullino DF; Delessert D; Eap CB; Preisig M; Baumann P

Year: 2002

Source type: Two case reports; smoking/tobacco context

DOI: 10.1097/00004850-200205000-00008

PMID: 11981356

Source access – 23 October 2026: Source destination was accessible when checked.

Bibliographic attribution or source identity cross-checked.

DOI – publisher access (access restrictions may apply)

[CA_P_28272498] The Differential Binding of Antipsychotic Drugs to the ABC Transporter P-Glycoprotein Predicts Cannabinoid-Antipsychotic Drug Interactions.

Original source / bibliographic reference

Authors: Brzozowska NI, de Tonnerre EJ, Li KM, Wang XS, Boucher AA, Callaghan PD, Kuligowski M, Wong A, Arnold JC.

Year: 2017

Source type: research-article; Journal Article

DOI: 10.1038/npp.2017.50

PMID: 28272498

Source access – 23 October 2026: Direct retrieval could not be fully verified; availability remains unresolved.

Bibliographic attribution or source identity cross-checked.

DOI – publisher access (access restrictions may apply)

PubMed Central – full-text access according to the literature database – Archive attribution confirmed by Europe PMC metadata. Direct retrieval was not fully verified here; access may require a browser check.

Europe PMC – full-text access according to the literature database – Listed as freely available HTML full text in the official Europe PMC metadata. Direct retrieval was not fully verified here.

[CA_P_39359160] Protocol for Cancloz: multicentre randomised, placebo-controlled, double-blind, parallel-group adaptive trial of cannabidiol for clozapine-resistant schizophrenia.

Original source / bibliographic reference

Authors: Siskind D, Bull C, Suetani S, Warren N, Suraev A, McGregor I, Kisely S, De Monte V, Trott M, Shine M, Moudgil V, Robinson G, Parker S, Krishnaiah R, Stedman T, Drummond A, Medland S, Iyer R, Baker A.

Year: 2024

Source type: research-article; Journal Article

DOI: 10.1192/bjo.2024.748

PMID: 39359160

Source access – 23 October 2026: Direct retrieval could not be fully verified; availability remains unresolved.

Bibliographic attribution or source identity cross-checked.

DOI – publisher access (access restrictions may apply)

PubMed Central – full-text access according to the literature database – Archive attribution confirmed by Europe PMC metadata. Direct retrieval was not fully verified here; access may require a browser check.

Europe PMC – full-text access according to the literature database – Listed as freely available HTML full text in the official Europe PMC metadata. Direct retrieval was not fully verified here.

Research as of 23 October 2026. Not all original full texts could be reviewed in full. Source accessibility and the strength of scientific evidence must be assessed separately. An accessible link does not establish medical approval; a bibliographic record with an abstract does not replace the original full text.

Drug search and explanation of the evidence · Guide: cannabinoids and medicines · Author and responsibility