OK to Try 6-MP When Azathioprine Is Not Tolerated

Azathioprine and 6-mercaptopurine (6-MP) can cause bone marrow toxicity, pancreatitis, fever, and rash. Adverse effects are often considered a class effect, which assumes that if one of these agents produces toxicity, the other will also.

That assumption was tested in the current retrospective, observational study of 149 patients with inflammatory bowel disease (82 with Crohn disease and 67 with ulcerative colitis) who were intolerant of azathioprine and subsequently treated with 6-MP. Researchers also conducted a meta-analysis involving 455 patients from 11 studies to assess tolerance of 6-MP in patients who did not tolerate azathioprine.

In the observational study, 58% of patients were able to tolerate treatment with 6-MP. This result varie…