Cetirizine

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: Cetirizine

Examples of brand names: Zyrtec [DE]

ATC code: R06AE07

Main use (for orientation): Allergies

Documented research summary

Cetirizine-associated psychosis case with rechallenge during chronic cannabis use; earlier head injury is another confounder. The case supports an association with cetirizine but does not prove a causal cannabinoid–cetirizine interaction.

Uncertainties and limitations

Original abstract assessed; full text technically inaccessible. Cannabis composition/amounts not isolated; no pharmacokinetic evidence. Do not automatically extrapolate to levocetirizine. Missing data do not establish safety.

Separately recorded findings

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

Cannabis; composition not quantified – insufficient data

Finding ID: B0460

Type of result: Adverse event during concomitant medication; pair causality not established

Observation: Psychotic symptoms with cetirizine, including a rechallenge finding, described.

Mechanism: Cetirizine-associated psychosis; possible cannabis influence not isolated

Study type: Single case with cetirizine rechallenge

Context studied: Young man with daily cannabis use and an earlier head injury.

Clinical interpretation: Confounded safety context, not an established general pair mechanism.

Limitations and uncertainties: Rechallenge supports cetirizine as a trigger but does not prove a cannabinoid–cetirizine interaction. No pharmacokinetic evidence; only the original abstract accessible, not complete case details.

Original sources for this finding: Cetirizine-induced psychosis in a young adult with erythema multiforme. [VE_MED_33547112]

References and access status

[VE_LABEL_D0343] Cetirizine Hydrochloride 10 mg Tablets – UK Summary of Product Characteristics

Original source / bibliographic reference

Authors: Respective marketing authorisation holder; regulatory product information

Year: Document version: see SmPC; accessed 2026

Source type: Product information / SmPC / US Prescribing Information

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

Bibliographic attribution or source identity cross-checked.

[VE_MED_33547112] Cetirizine-induced psychosis in a young adult with erythema multiforme.

Original source / bibliographic reference

Authors: Croitoru D, Brooks SG, Piguet V, MacGillivray L.

Year: 2021

Source type: Journal Article; Case Reports; case-report

DOI: 10.1136/bcr-2020-241393

PMID: 33547112

Source access – 23 October 2026: Automated direct retrieval was restricted; this does not establish that the link is broken.

Bibliographic attribution or source identity cross-checked.

PubMed – bibliographic reference / abstract

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