6-thioguanine--efficacy and safety in chronic active Crohn's disease

Aliment Pharmacol Ther. 2003 Feb 15;17(4):503-8. doi: 10.1046/j.1365-2036.2003.01440.x.


Background: : Azathioprine and mercaptopurine are commonly used in chronic active Crohn's disease. They share the disadvantage of a delayed onset of action and potentially serious side-effects, and are metabolized to thioguanine nucleotides which are thought to be the active metabolites. The direct use of 6-thioguanine may offer a more rapid and safer alternative. We conducted an open prospective study to investigate the efficacy and safety of 6-thioguanine in chronic active Crohn's disease.

Methods: : Thirty-seven patients with chronic active Crohn's disease and a Crohn's disease activity index of > 150 were enrolled in this study. Inclusion criteria were steroid dependence (n = 19), steroid refractoriness (n = 9) and/or intolerance (n = 16) or refractoriness (n = 6) to azathioprine. Patients were treated with 40 mg/day of 6-thioguanine for 24 weeks; a dose escalation to 80 mg was allowed at week 12. Remission was defined as a Crohn's disease activity index of < 150 associated with a decrease of > 70 points; response was defined as a decrease of > 70 points in the Crohn's disease activity index.

Results: : In the intention-to-treat analysis, 13 of 37 patients achieved remission (35%). Twelve of these 13 patients achieved remission after 4 weeks. Fifty-seven per cent of patients (21/37) achieved a response. The mean Crohn's disease activity index decreased from 284 +/- 74 to 153 +/- 101. 6-Thioguanine was more effective in azathioprine-intolerant than in azathioprine-refractory patients. Twelve of 16 patients intolerant to azathioprine tolerated 6-thioguanine. Adverse events included phototoxicity, pancreatitis, headache, nausea, alopecia, arthralgia, minor infections and reversible elevation of transaminases. Six patients required discontinuation of medication, two because of leucopenia.

Conclusions: : In this patient group with chronic active Crohn's disease, 6-thioguanine appeared to be effective with acceptable short-term toxicity, but long-term controlled trials are clearly needed to further define its role.

Publication types

  • Evaluation Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Chronic Disease
  • Crohn Disease / drug therapy*
  • Dose-Response Relationship, Drug
  • Female
  • Humans
  • Immunosuppressive Agents / administration & dosage*
  • Immunosuppressive Agents / adverse effects
  • Male
  • Mercaptopurine / administration & dosage*
  • Mercaptopurine / adverse effects
  • Middle Aged
  • Prospective Studies
  • Treatment Outcome


  • Immunosuppressive Agents
  • Mercaptopurine