Optimization of azathioprine dose in combined treatment with anti-TNF-alpha in inflammatory bowel disease

Introduction: The dose of thiopurine drugs in combined treatments with anti-TNF in inflammatory bowel disease (IBD) has not been clearly established. The purpose of this study is to assess whether the dose of azathioprine influences clinical and biochemical response/remission rates, and anti-TNF drug levels/antibody formation. Material and methods: Patients with IBD on combined maintenance treatment with azathioprine and infliximab or adalimumab were selected. Based on the dose of azathioprine, two groups were defined (standard: 2-2.5 mg/kg/day; and decreased: less than 2 mg/kg/day). Results: In the IFX group, there were no statistically significant differences (p =0.204) in the rates of remission (39% vs 41.3%), response (10% vs 21.7%) or failure (51.5% vs 37%) depending on the dose of thiopurine drugs. No differences were found between AZA-dose dependent IFX levels (2.46 vs 3.21 mu g/mL; p= 0.211). In the adalimumab group, there were no statistically significant differences (p= 0.83) in the rates of remission (66% vs 56%), response without remission (15.38% vs 25%) or failure (18% vs 18%) depending on the dose of thiopurines. With respect to ADA-levels, no differences were found in both groups (7.69 vs 8.23 mu g/mL; p= 0.37). Conclusion: In our experience, no statistically significant differences were found in either anti-TNF levels or clinical-biological response/remission rates based on doses of azathioprine. (C) 2020 Elsevier Espana, S.L.U. All rights reserved.