Background: Recent studies suggest that subcutaneous infliximab is effective and safe for treating patients with inflammatory bowel disease. Real-world studies with larger cohorts are needed to confirm the efficacy of subcutaneous treatment.

Aims: The aim was to assess real-world treatment persistence, clinical outcomes, infliximab concentrations, and treatment safety after switching from intravenous to subcutaneous infliximab treatment with patients with inflammatory bowel disease.

Methods: This retrospective register-based study included patients with inflammatory bowel disease who were in clinical remission and switched from intravenous infliximab maintenance therapy to subcutaneous infliximab in two tertiary centers.

Results: A total of 274 patients (104 Crohn's disease and 170 ulcerative colitis) were included. After the switch, the treatment persistence at 12 months was 94.8% in patients with Crohn's disease and 88.8% in patients with ulcerative colitis. Only 11.3% (n = 31) of the patients discontinued the treatment during 79-week median follow-up. Compared to the baseline, no change occurred in clinical disease activity at the time points of 3, 6, and 12 months, based on the Harvey-Bradshaw Index or partial Mayo Score (p = 0.792 and p = 0.426, respectively). Infliximab median concentrations were higher (p < 0.0001) during subcutaneous treatment (16.75 µg/ml) compared to the intravenous treatment median trough levels before the switch (6.71 µg/ml). In total, 15.0% (n = 41) of the patients reported adverse events.

Conclusion: Switching to subcutaneous infliximab maintenance therapy was associated with high treatment persistence, a stable disease course, increased infliximab concentrations, and an acceptable safety profile.