Forsigtighed tilrådes, hvis leflunomid gives samtidig med lægemidler, – bortset fra NSAID - præparater – der metaboliseres via CYP2C9, som f. eks. fenytoin, warfarin, phenprocoumon og tolbutamid.
Caution is advised when leflunomide is given together with drugs, other than NSAIDs, metabolised by CYP2C9 such as phenytoin, warfarin, phenprocoumon and tolbutamide.