Danger in Administering Azathioprine and Mercaptopurine Toge

A recent Institute for Safety Medication Practices report alerted readers to the possibility of patient death if azathioprine, an immunosuppressant, and mercaptopurine, an antimetabolite, are given together. The report points out that mercaptopurine is a metabolite of azathioprine, and so if the two drugs are taken together, the patient is receiving duplicate therapy. ISMP cites a case in which a patient with a history of Crohn's disease took the medications together, as prescribed, and later developed profound myelosuppression and severe sepsis, and died. ISMP notes that many drug information software programs do not warn of this particular therapeutic duplicaton. They suggest that hospitals ask that their drug information computer programs be modified to show this information if it doesn't already appear, and that drug reference materials also include a warning about this potentially fatal drug combination.