Background: Inflammatory bowel disease (IBD) is a collection of chronic, recurrent inflammatory illnesses of the gastrointestinal system, including Crohn's disease (CD). Infliximab is one of the biological medications used to treat CD. Therapeutic drug monitoring has evolved as a treatment in IBD, aiming to optimize benefit while meeting more demanding, objective end criteria. Objective: To determine the achievement of target trough level (TL), develop anti-drug antibodies (ADAs) to infliximab, assess response to therapy, and study TL relations with different variables. Methods: The present study was cross-sectional and conducted from May 2022 to November 2022. It included 40 CD patients allotted into 2 groups: group 1 patients achieved the TL target, and group 2 patients did not achieve the TL target. Results: Twenty-two patients achieved target TL, while 18 patients did not. Dose escalation is recommended for 11 patients, switching therapy for 15 patients, and continuing the same dosage regimen for 14 patients. In addition, erythrocyte sedimentation rate, C-reactive protein, serum calprotectin and ADAs were significantly lower in patients who achieved target infliximab TL. Only serum calprotectin can be used to predict the achievement of the target TL of infliximab. Conclusions: Therapeutic drug monitoring of infliximab to determine the TL and ADAs can help to explain why some patients do not respond to this drug. Serum calprotectin may be used as a novel marker to predict the TL and response to infliximab.
