Use of 6-mercaptopurine in patients with inflammatory bowel disease previously intolerant of azathioprine

Both azathioprine and its active metabolite, 6-mercaptopurine, are of benef it in the treatment of inflammatory bowel disease, either in resistant case s, or for their steroid-sparing effect. Azathioprine treatment is limited i n some patients by hypersensitivity reactions or other side effects. We rep ort our experience in 11 patients previously unable to tolerate azathioprin e for a variety of reasons, who were switched to 6-mercaptopurine. Of seven patients with ulcerative colitis and four patients with Crohn's disease wh o were treated with 6-mercaptopurine following failed azathioprine therapy, six were able to successfully tolerate the substitute medication, with goo d response. Where patients have previously been intolerant of azathioprine yet ongoing indications for immunosuppressive therapy remain, a trial of 6- mercatopurine may be warranted. Given the similar efficacies of the two dru gs in inflammatory bowel disease, these findings also favor the use of 6-me rcaptopurine rather than the parent compound as initial therapy.