Caution is advised when leflunomide is given together with drugs, other than NSAIDs, metabolised by CYP2C9 such as phenytoin, warfarin, phenprocoumon and tolbutamide.
Ettevaatus on vajalik leflunomiidi manustamisel koos teiste (välja arvatud MSPVA- d) preparaatidega, mis metaboliseeruvad CYP2C9 abil: fenütoiin, varfariin, fenprokumoon ja tolbutamiid.