Promethazine

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: Promethazine

Examples of brand names: Atosil [DE]

ATC code: R06AD02

Main use (for orientation): Agitation; allergy

Documented research summary

Separate promethazine and THC comparator arms do not establish co-administration. Additive depression remains theoretical.

Uncertainties and limitations

Additive sedation is plausible label-based risk context, not a measured pair-specific enhancement factor.

Research is limited to the specified date and protocol; it is not globally exhaustive. Brand names and authorisations do not constitute a complete current market overview.

Structured assessment

Category: Theoretical context

Cannabinoid scope: 28 register names in the documented search family; neither 28 individual clinical trials nor a blanket assessment of all cannabinoids.

Evidence status: Theoretical plausibility; no verified clinical pair effect

Mechanism / drug context: Promethazine: sedating antihistamine; hepatic breakdown.

Type of supporting material: Medicine information and documented individual review; no positive pair trial

Clinical interpretation: Requires individual assessment by a doctor or pharmacist. Lack of evidence does not establish safety; no dosage or discontinuation advice is provided.

Context: Promethazine hydrochloride injection; active racemate, not a prodrug. Oral comparator experiment considered separately.

Drug context and gaps in search results are not measured interactions. The source role below describes which statement the source actually supports.

Source role [CA_L_D0137]: Drug context

Statement supported: Supports dosage form, metabolism and/or known risks; alone, it does not substantiate a cannabinoid–drug pair finding.

Source: PROMETHAZINE HYDROCHLORIDE (PROMETHAZINE HYDROCHLORIDE) INJECTION [HENRY SCHEIN, INC.] [CA_L_D0137]

Source role [CA_P_29635857]: Scope distinction / context

Statement supported: Promethazine and THC in separate comparator arms.

Source: Effect profile of paracetamol, Δ9-THC and promethazine using an evoked pain test battery in healthy subjects. [CA_P_29635857]

Scope of review: Individual research with documented title/abstract screening and targeted review of original sections. This is not exhaustive evidence that interactions are absent.

Unresolved source question: The complete stored individual review, label review, literature screening, conclusion and uncertainties were read. Targeted sections of original information were rechecked; no claim is made that all product information or full texts were completely revalidated.

Separately recorded findings

No separately substantiated finding for this drug–cannabinoid pair is recorded within the documented scope of review. This does not prove that no such study exists anywhere or that the combination is safe.

References and access status

[CA_L_D0137] PROMETHAZINE HYDROCHLORIDE (PROMETHAZINE HYDROCHLORIDE) INJECTION [HENRY SCHEIN, INC.]

Original source / bibliographic reference

Authors: Henry Schein, Inc.

Year: 2026

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.

[CA_P_29635857] Effect profile of paracetamol, Δ9-THC and promethazine using an evoked pain test battery in healthy subjects.

Original source / bibliographic reference

Authors: van Amerongen G, Siebenga P, de Kam ML, Hay JL, Groeneveld GJ.

Year: 2018

Source type: Randomized Controlled Trial; Journal Article

DOI: 10.1002/ejp.1222

PMID: 29635857

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)

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