K Clarkston et al. JPGN 2019; 69: 68-74. This pediatric study with 72 children/young adults with Crohn’s disease examined infliximab trough levels; 70 received infliximab monotherapy & 88% received “standard” dose of 5 mg/kg

Key findings:

• Infliximab level ≥18 mcg/mL at week 6 was strongly associated with clinical and biologic response as well as achieving an infliximab level ≥5 mcg/mL at week 14 (AUC 0.85).
• A week 6 level ≥18 mcg/mL had 82% sensitivity, 82% specificity, 56% PPC, and 94% NPV  for having a therapeutic level at 4th infusion.
• Median infliximab levels for clinical responders was 27.8 mcg/mL at 2nd infusion and 14 mcg/mL at 3rd infusion.
• The authors reported that only 22% of their cohort achieved a week 14 infliximab level ≥5 mcg/mL. The median infliximab level at this time point was 2.1 mcg/mL.

My take: In this study, the standard dose of infliximab (5 mg/kg) was not adequate in ~80% of patients in achieving a therapeutic trough level.  If using the standard low-dose, it may be worthwhile to check a trough level prior to 3rd infusion or at week 10 to help determine if the level will be sufficient to start maintenance treatment at week 14 or whether an earlier infusion is warranted.

Related blog posts:

• Is Standard Infliximab Dose Too Low in Pediatrics?
• Can Therapeutic Drug Monitoring with Monotherapy Achieve Similar Results as Combination Therapy for IBD? | gutsandgrowth

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Disclaimer: These blog posts are for educational purposes only. Specific dosing of medications/diets (along with potential adverse effects) should be confirmed by prescribing physician/nutritionist.  This content is not a substitute for medical advice, diagnosis or treatment provided by a qualified healthcare provider. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a condition.