Leflunomide

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: Leflunomide

Examples of brand names: Arava [EU/DE]

ATC code: L04AK01

Main use (for orientation): Rheumatoid arthritis

Documented research summary

No direct cannabinoid pair study identified. Classification in an interaction review does not replace a measured clinical finding.

Uncertainties and limitations

Review full text/individual primary evidence not accessibly evaluated.

Do not count leflunomide and teriflunomide as chemically identical substances.

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: Leflunomide is converted to active teriflunomide; possible overlapping hepatic burden.

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: Oral Arava/leflunomide, US label dated 4 June 2025; indication, contraindications and sections 5.2, 7 and 12 read. Prodrug with active teriflunomide; formation via several CYP pathways (in vitro 1A2/2C19/3A4), but teriflunomide itself is not a CYP substrate according to the label. Long metabolite half-life, biliary excretion and enterohepatic persistence. Teriflunomide inhibits CYP2C8/OAT3/BCRP/OATP1B1/1B3 and may induce CYP1A2. Warning about additional hepatotoxicity.

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

Source role [RLABEL_D0027]: Drug context

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

Source: ARAVA (LEFLUNOMIDE) TABLET, FILM COATED [SANOFI-AVENTIS U.S. LLC] [RLABEL_D0027]

Source role [BMED42841466]: Scope distinction / context

Statement supported: Secondary review used as a research lead; severity classification not adopted as primary evidence.

Source: The Pharmacokinetic and Pharmacodynamic Drug-drug Interaction Potential of Cannabidiol. [BMED42841466]

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

[RLABEL_D0027] ARAVA (LEFLUNOMIDE) TABLET, FILM COATED [SANOFI-AVENTIS U.S. LLC]

Original source / bibliographic reference

Authors: Regulatory product information; respective marketing authorisation holder

Year: 2025

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.

[BMED42841466] The Pharmacokinetic and Pharmacodynamic Drug-drug Interaction Potential of Cannabidiol.

Original source / bibliographic reference

Authors: Keller GA, Aimar JA.

Year: 2026

Source type: Publication; title and abstract reviewed

DOI: 10.2174/0118723128411684251029100517

PMID: 42841466

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

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