Technical and regulatory perspective on acid stage dissolution assessed via optical coherence tomography (Part 1: Release Scenario).

Enteric coating ensures a targeted release of active pharmaceutical ingredients (APIs) by protecting them from premature dissolution in the stomach. The effectiveness of such coating depends on its thickness and integrity, which are critical for achieving the desired acid protection. This study explores the use of Optical Coherence Tomography (OCT) as an innovative and non-destructive alternative to traditional acid stage dissolution testing performed by directly measuring the coating thickness. Three enteric coating materials (Acryl-Eze®, Aquarius™ Control ENA, and Nutrateric®) were tested in two manufacturing batches to evaluate operator variability. OCT was used to measure the coating thickness, which was correlated with the acid stage dissolution testing and established critical thicknesses of 68 µm for Acryl-Eze®, 69 µm for Aquarius™ Control ENA, and 65 µm for Nutrateric®. These specifications ensure compliance with the pharmacopeial performance criteria for acid protection and can be implemented into regulatory frameworks as part of product release protocols in the dossier. By demonstrating the agreement between the results of OCT-based thickness measurements and the pharmacopeial dissolution testing, this work underscores the potential of OCT to be recognized in regulatory contexts as a tool for enhanced production efficiency and quality assurance in manufacturing enteric-coated oral dosage forms.