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Mercaptopurine treatment should be considered in azathioprine intolerant patients with inflammatory bowel disease

U Hindorf1, M Johansson, A Eriksson

  • 1Department of Gastroenterology and Nutrition, University Hospital, Lund, Sweden. ulf.hindorf@skane.se

Alimentary Pharmacology & Therapeutics
|February 3, 2009
PubMed
Abstract

Insights

Switching to mercaptopurine can be successful for many patients with inflammatory bowel disease experiencing azathioprine intolerance. About half of patients tolerate mercaptopurine, particularly those with prior hepatotoxicity or arthralgia/myalgia.

Area of Science:

  • Gastroenterology
  • Pharmacology
  • Clinical Therapeutics

Background:

  • Adverse drug reactions (ADRs) are a major cause of treatment failure in inflammatory bowel disease (IBD) patients on thiopurines.
  • Smaller studies suggest switching from azathioprine (AZA) to mercaptopurine (MP) can be effective for AZA-intolerant patients.

Purpose of the Study:

  • To evaluate the long-term outcomes of switching to mercaptopurine in a large cohort of IBD patients with a history of azathioprine intolerance.

Main Methods:

  • Retrospective review of medical records for 135 patients (Crohn's disease n=88; ulcerative colitis n=47) who switched from azathioprine to mercaptopurine.
  • Analysis of tolerance, adverse events, and patient characteristics, including thiopurine methyltransferase (TPMT) activity.

Main Results:

  • 70 patients (52%) tolerated mercaptopurine long-term (median 736 days).
  • 65 patients discontinued mercaptopurine due to adverse events (median 25 days).
  • Higher tolerance rates for mercaptopurine were observed in patients with prior azathioprine-induced hepatotoxicity (71%) or arthralgia/myalgia (68%).
  • Mercaptopurine-intolerant patients had a higher prevalence of prior abdominal surgery (60% vs 39%).
  • Mercaptopurine-tolerant patients exhibited higher TPMT activity (13.2 vs 11.8 U/mL; P=0.04).

Conclusions:

  • A trial of mercaptopurine is recommended for IBD patients experiencing azathioprine intolerance, given the substantial tolerance rate (approx. 50%).
  • Patients with specific adverse events like hepatotoxicity or arthralgia/myalgia during azathioprine therapy may have a better outcome with mercaptopurine.
  • Higher TPMT activity and lower rates of prior abdominal surgery may predict successful mercaptopurine tolerance.

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