Meta-analysis: the efficacy of azathioprine and mercaptopurine in ulcerative colitis

Aliment Pharmacol Ther. 2009 Jul 1;30(2):126-37. doi: 10.1111/j.1365-2036.2009.04023.x. Epub 2009 Apr 15.


Background: Debate exists regarding to whether thiopurine therapy is as effective in ulcerative colitis (UC) as it is in Crohn's disease.

Aim: To review systematically the efficacy of azathioprine (AZA) and mercaptopurine (MP) in UC, and to conduct a meta-analysis of randomized clinical trials evaluating the efficacy of AZA/MP for the induction or maintenance of UC clinical remission.

Selection of studies: Evaluating AZA/MP for induction and/or maintenance of clinical remission of UC. Randomized-controlled-trials comparing AZA/MP with placebo/5-aminosalicylates were included in the meta-analysis.

Search strategy: Electronic and manual. Study quality: Independently assessed by two reviewers.

Data synthesis: By 'intention-to-treat'.

Results: Thirty noncontrolled studies (1632 patients) were included in the systematic review. Mean efficacy of AZA/MP was 65% for induction and 76% for maintenance of the remission. Seven controlled studies were included in the meta-analysis. (i) Induction of remission: four studies (89 AZA/MP-treated patients) showed mean efficacy of 73% vs. 64% in controls (OR = 1.59; 95% CI = 0.59-4.29). (ii) Maintenance of remission: six studies (124 AZA/MP-treated patients) showed mean efficacy of 60% vs. 37% in controls (OR = 2.56; 95% CI = 1.51-4.34). When only studies comparing AZA/MP vs. placebo were considered, OR was 2.59 (95% CI = 1.26-5.3), absolute risk reduction was 23% and number-needed-to-treat (NNT) to prevent one recurrence was 5.

Conclusion: Thiopurine drugs (AZA/MP) are more effective than placebo for the prevention of relapse in UC, with an NNT of 5 and an absolute risk reduction of 23%.

Publication types

  • Comparative Study
  • Meta-Analysis
  • Research Support, Non-U.S. Gov't
  • Systematic Review

MeSH terms

  • Azathioprine / therapeutic use*
  • Colitis, Ulcerative / drug therapy*
  • Colitis, Ulcerative / prevention & control
  • Humans
  • Immunosuppressive Agents / therapeutic use*
  • Mercaptopurine / therapeutic use*
  • Randomized Controlled Trials as Topic
  • Remission Induction
  • Secondary Prevention
  • Treatment Outcome


  • Immunosuppressive Agents
  • Mercaptopurine
  • Azathioprine