Technical and regulatory perspective on acid stage dissolution assessed via optical coherence tomography (Part 2:...

Stability testing of pharmaceuticals is a critical aspect of drug development, approval and commercialization. Some active pharmaceutical ingredients (APIs) require protection against degradation in the acidic environment of the stomach, which can be achieved by using enteric polymers as coating. The performance of such coating depends not only on its thickness but also on its stability over time, since the protective function must be maintained throughout the product's shelf life. This study evaluates the use of Optical Coherence Tomography (OCT) as an innovative, non-destructive alternative to traditional acid-stage dissolution testing, which is performed by directly measuring the coating thickness during stability testing. Three enteric coating materials (Acryl-Eze®, Aquarius™ Control ENA and Nutrateric®) were tested over 6-month accelerated and 12-month long-term stability periods following ICH Q1A (R2) Guidelines. The coating thickness measured via OCT remained consistent and correlated with the degree of protection against acid-stage dissolution. All coating formulations met the acceptance criteria established in USP<711>A₁. However, significant variability was observed in the Aquarius™ Control ENA and Nutrateric® formulations, posing a challenge for the regulatory submission. Such variations require strategic assessment by the Marketing Authorization Holder (MAH) to ensure compliance with the regulatory expectations. This study demonstrates equivalence between OCT-based thickness measurements in stability testing and pharmacopeial dissolution testing, highlighting OCT as a viable analytical tool for regulatory agencies to recognize. Establishing this equivalence can enhance overall compliance, improve quality assurance and reduce the required laboratory resources.