- If the patient is not currently using corticosteroids, antimalarials, methotrexate, MMF, or azathioprine, the last dose (in case of previous use) must be at least 4 weeks prior to the 1st dose of study drug. For leflunomide, the stop date must be at least 8 weeks before the 1st dose of study drug unless an adequate cholestryamine washout has been performed. If cholestyramine washout is performed, the last use of leflunomide must be at least 4 weeks before the 1st dose of study drug.