Specific interaction studies have not been performed. Lactulose or similar preparations which lower stool pH: possible reduction of mesalazine release from granules due to decreased pH caused by bacterial metabolism of lactulose. In patients who are concomitantly treated with azathioprine, 6-mercaptopurine or thioguanine, a possible increase in the myelosuppressive effects of azathioprine, 6-mercaptopurine or thioguanine should be taken into account. There is weak evidence that mesalazine might decrease the anticoagulant effect of warfarin.