Dynamic vapor sorption for quality assessment of pharmaceutical coatings: a case study in enteric protection

Abstract

This study investigates the performance of different enteric coating systems by integrating dynamic vapor sorption (DVS), optical coherence tomography (OCT), and acid-stage dissolution testing to evaluate moisture sensitivity, structural integrity, and acid resistance of coated pharmaceutical tablets. Omeprazole-containing tablets were coated with three commercially available enteric systems and analyzed using DVS to assess sorption kinetics under controlled humidity and temperature conditions. OCT was employed to non-destructively evaluate coating thickness and uniformity. Functional performance was determined via acid-stage dissolution testing following FDA guidelines for delayed-release formulations. The DVS results revealed marked differences in moisture uptake behavior among the coatings, while OCT imaging identified variability in coating distribution, both of which were found to correlate with dissolution outcomes. Coatings with lower hygroscopicity and more consistent thickness profiles demonstrated acid resistance. These findings underscore the value of combining DVS and OCT as complementary analytical tools for the comprehensive evaluation of enteric coatings, enabling improved formulation design and quality control aligned with Quality by Design (QbD) principles.