leflunomide and duloxetine: label evidence and limits

The leflunomide label names duloxetine among CYP1A2 substrates whose exposure may decrease. It attributes this effect to teriflunomide, leflunomide’s active metabolite.

Which products this evidence covers

Oral leflunomide tablets; CYP1A2 substrate interaction.

What this finding does and does not establish

The label supports this exposure warning. It does not establish CDI’s moderate category or predict the effect for an individual patient.

Supporting label passage

Teriflunomide, the active metabolite of leflunomide, may be a weak inducer of CYP1A2 in vivo . In patients taking leflunomide, exposure of drugs metabolized by CYP1A2 (e.g., alosetron, duloxetine, theophylline, tizanidine) may be reduced. Monitor these patients and adjust the dose of the concomitant drug(s) metabolized by CYP1A2 as required [see Clinical Pharmacology (12.3)] .

Read the product label on DailyMed. Section: 7 Drug Interactions — CYP1A2 substrates. Compared label version 8, dated 2024-08-20.

How this brief was prepared

This brief uses an AI-assisted source comparison dated 2026-10-16. The label version and supporting passage were checked again on 2026-10-25. Independent clinical review has not been recorded. The comparison does not validate CDI's severity category or determine individual treatment.

Discuss your exact medicines with your pharmacist

Ask whether the cited formulation and route apply to your products and circumstances. Confirm medication decisions with your pharmacist or prescriber before changing treatment.

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