Long-term outcome of using allopurinol co-therapy as a strategy for overcoming thiopurine hepatotoxicity in treating inflammatory bowel disease

Aliment Pharmacol Ther. 2008 Sep 15;28(6):734-41. doi: 10.1111/j.1365-2036.2008.03782.x.

Abstract

Background: Hepatotoxicity results in the withdrawal of thiopurines drugs, azathioprine (AZA) and mercaptopurine (MP), in up to 10% of patients with inflammatory bowel disease. Our group previously demonstrated that allopurinol with AZA/ciclosporin/steroid 'triple therapy' improved renal graft survival.

Aim: To confirm the hypothesis that allopurinol may alleviate thiopurine hepatotoxicity by similar mechanisms as proposed in our renal study.

Methods: Unselected patients with acute thiopurine hepatotoxicity were offered allopurinol co-therapy with low-dose AZA or MP. The starting AZA/MP dose was determined by thiopurine methyltransferase (TPMT) activity (two patients were intermediate TPMT); then this dose was reduced to 25% for allopurinol co-therapy. Response to treatment was assessed by clinical severity indices, endoscopy and blood tests.

Results: Of 11 patients (three Crohn's disease, eight ulcerative colitis) treated, nine (82%) remain in long-term remission (median 42 months) with normal liver tests. One patient also successfully bypassed flu-like symptoms. Two stopped: one nausea, one abnormal liver function (stealosis on biopsy). Leucopenia occurred in two cases and resolved with minor dose reductions.

Conclusions: Allopurinol co-therapy with low-dose AZA/MP can alleviate thiopurine hepatotoxicity. It appears safe and effective for long-term use, but requires monitoring for myelotoxicity. Assessing the TPMT activity helps tailor the AZA/MP doses.

MeSH terms

  • Adult
  • Aged
  • Allopurinol / therapeutic use*
  • Chemical and Drug Induced Liver Injury / drug therapy*
  • Dose-Response Relationship, Drug
  • Drug Synergism
  • Drug Therapy, Combination
  • Drug-Related Side Effects and Adverse Reactions / prevention & control
  • Enzyme Inhibitors / therapeutic use*
  • Female
  • Humans
  • Immunosuppressive Agents / adverse effects*
  • Immunosuppressive Agents / metabolism
  • Inflammatory Bowel Diseases / drug therapy*
  • Inflammatory Bowel Diseases / enzymology
  • Male
  • Mercaptopurine / adverse effects*
  • Mercaptopurine / analogs & derivatives
  • Mercaptopurine / metabolism
  • Methyltransferases / metabolism
  • Middle Aged
  • Retrospective Studies
  • Treatment Outcome

Substances

  • Enzyme Inhibitors
  • Immunosuppressive Agents
  • Allopurinol
  • Mercaptopurine
  • Methyltransferases
  • thiopurine methyltransferase