Abstract
BACKGROUND: There are limited data regarding the impact of body mass index (BMI) on pharmacokinetics in patients with inflammatory bowel disease (IBD) treated with vedolizumab (VDZ) or ustekinumab (UST). The aim of the study was to investigate the association of BMI with VDZ and UST concentrations in IBD.
METHODS: This single-center, retrospective study included consecutive patients with IBD who received intravenous (iv) VDZ or UST and underwent therapeutic drug monitoring (TDM) from November 2016 to March 2023. We assessed the correlation of BMI with drug concentrations using Spearman's rank test.
RESULTS: The study population consisted of 170 patients; 89 (52%) patients received iv VDZ [44% Crohn's disease (CD)] and 81 received UST (81% CD). There was an inverse correlation of baseline BMI [ρ: -0.321; 95% confidence interval (CI) -0.534 to -0.070; P = .011] and BMI at first TDM (ρ: -0.253; 95% CI, -0.462 to -0.018; P = .031) with UST concentration at first TDM. Regarding the latter, subgroup analyses revealed that this correlation referred only to patients with Crohn's disease (CD) (ρ: -0.293; 95% CI, -0.515 to -0.035; P = .023) or patients with IBD on standard UST dosing (ρ: -0.369; 95% CI, -0.616 to -0.055; P = .019). In contrast, there was no correlation of BMI with VDZ concentrations. Multivariable linear regression analysis identified higher BMI at first TDM as an independent variable associated with lower UST concentrations (B: -0.408; 95% CI, -0.930 to -0.217; P = .002).
CONCLUSION: This study demonstrated an inverse correlation between BMI and UST concentrations in patients with CD or patients with IBD on standard UST dosing, suggesting the need for closer TDM and dose adjustments to ensure optimal drug exposure in these patients with higher BMI.