What are the optimal trough levels for Infliximab (infliximab) in the treatment of Crohn's disease?

From the Guidelines

The optimal trough level for infliximab in Crohn's disease is generally considered to be between 3-7 μg/mL during maintenance therapy, as evidenced by the TAXIT study 1. This target range is associated with improved clinical outcomes, including increased rates of clinical remission and mucosal healing. For patients with active disease requiring induction, higher trough levels may be more appropriate to achieve mucosal healing, but the exact target range is not well established. Infliximab trough levels should be measured just before the next scheduled infusion, typically at 8 weeks for standard maintenance dosing. If a patient shows inadequate response to therapy, trough levels below 3 μg/mL often indicate the need for dose intensification, which can be achieved by increasing the dose or shortening the interval between infusions. When interpreting trough levels, it's essential to check for anti-drug antibodies, as their presence may necessitate switching to another biologic agent. Regular monitoring of trough levels, especially when clinical response is suboptimal, allows for personalized dosing strategies that maximize efficacy while minimizing the risk of immunogenicity and adverse effects. Key considerations in interpreting trough levels include:

• The presence of anti-drug antibodies, which may necessitate switching to another biologic agent
• The clinical context, including the patient's disease activity and previous response to therapy
• The potential for dose intensification or interval shortening to improve clinical outcomes
• The importance of regular monitoring to optimize long-term outcomes in Crohn's disease management, as supported by the british society of gastroenterology consensus guidelines 1.

From the Research

Optimal Trough Levels for Infliximab in Crohn's Disease

• The optimal trough levels for infliximab in Crohn's disease have been studied in several research papers 2, 3, 4, 5, 6.
• A study published in 2025 found that subcutaneous infliximab trough concentrations were significantly higher in patients with mucosal healing (24.1 vs. 16.9 μg/mL) and transmural healing (26.0 vs. 20.5 μg/mL) than in those without 2.
• The same study identified threshold values of 17.5 μg/mL for mucosal healing and 30.3 μg/mL for transmural healing using ROC analysis 2.
• Another study published in 2013 found that infliximab trough levels >3 μg/mL were associated with a decreased risk of treatment failure 3.
• A 2019 study found that therapeutic drug monitoring by measuring infliximab trough levels and antibodies to infliximab was useful in optimizing treatment in inflammatory bowel disease 4.
• A 2018 study found that infliximab concentration thresholds of 2.2,9.7, and 9.8 μg/mL were related to biochemical, endoscopic, and histologic remission, respectively 5.
• A 2023 study found that early infliximab trough levels predicted the long-term efficacy of infliximab, with a threshold value of 4.5 μg/mL at week 6 and 4.0 μg/mL at week 14 6.

Factors Associated with Optimal Trough Levels

• Several factors have been associated with optimal trough levels, including:
  • Higher infliximab trough concentrations 2, 5
  • Presence of antibodies against infliximab 3
  • Need for corticosteroids 3
  • Concomitant use of immunosuppressants 3
  • Early infliximab trough levels 6

Clinical Implications

• The optimal trough levels for infliximab in Crohn's disease may vary depending on the treatment goal and patient population 2, 5.
• Therapeutic drug monitoring by measuring infliximab trough levels and antibodies to infliximab may be useful in optimizing treatment in inflammatory bowel disease 4.
• Early infliximab trough levels may predict the long-term efficacy of infliximab 6.