Safety and Effectiveness of Long-term Allopurinol – Thiopurine Maintenance Treatment in In fl ammatory Bowel Disease

Background: Thiopurines are the mainstay of conventional maintenance therapy in in fl ammatory bowel disease (IBD). Unfortunately, up to 50% of patients discontinue immunosuppressive therapy within 2 years due to intolerance or lack of ef fi cacy. Allopurinol with low-dose thiopurine can optimize thiopurine metabolism for IBD patients with preferential shunting toward 6-methyl mercaptopurine (6-MMP) formation. The aim of this study was to assess long-term maintenance effectiveness and tolerability of allopurinol-thiopurine therapy in a larger multicenter cohort of IBD patients. Methods: Enrolled patients who failed monotherapy with thiopurines due to a skewed metabolism were subsequently treated with a combination therapy of allopurinol and low-dose thiopurine. Adverse events were monitored and therapeutic adherence was assessed. Seventy-seven IBD patients were enrolled with a mean follow-up of 19 months. Results: The median 6-thioguanine nucleotide concentration increased from 145 during monotherapy to 271 pmol/8 · 10 8 red blood cell (RBC) after at least 8 weeks of combination therapy while reducing the thiopurine dosage ( P , 0.001). In contrast, median 6-MMP concentrations decreased from 10,110 to 265 pmol/8 · 10 8 RBC ( P , 0.001). Leukopenia occurred in 12 patients (16%), requiring dose adaptation. Liver test abnormalities normalized in 81% of patients after the addition of allopurinol. Sixteen (21%) patients had to discontinue combination therapy. The percentage of patients still using combination therapy at 6, 12, 24, and 60 months was 87%, 85%, 76%, and 65%, respectively. Conclusions: Long-term combination therapy with allopurinol and low-dose thiopurines is an effective and well-tolerated treatment in IBD patients with a skewed thiopurine metabolism. (In fl amm Bowel Dis 2013;19:363 – 369) safety and effectiveness of concomitant use of thiopurines and allopurinol in IBD patients who failed weight-based conventional thiopurines.

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