Solid-state interactions at the core-coat interface: physicochemical characterization of enteric-coated omeprazole...

Area of Science:

• Pharmaceutical Sciences
• Materials Science
• Analytical Chemistry

Background:

• Conventional methods for characterizing functional coatings include electron microscopy, various spectroscopy techniques (Raman, NIR, fluorescence), and imaging (terahertz, NMR).
• Investigating the physicochemical stability and coating integrity of enteric-coated drug delivery systems is crucial for ensuring therapeutic efficacy.
• Omeprazole pellets with enteric coatings are commonly prepared using extrusion-spheronization or drug layering, with potential challenges at the coat-core interface.

Purpose of the Study:

• To highlight the utility of fluorescence microscopy for assessing the physicochemical stability and coating integrity of enteric-coated omeprazole pellets.
• To examine the nature of the coat-core interface and the potential formation of an in situ interfacial layer.
• To validate a new fracturing technique for solid pellet structure characterization using fluorescence microscopy.

Main Methods:

• Fluorescence microscopy was employed to investigate coating integrity and interfacial phenomena.
• High-performance liquid chromatography (HPLC), Nuclear Magnetic Resonance (NMR), and Differential Scanning Calorimetry (DSC) were used for chemical and thermal analysis.
• A novel fracturing technique was developed and validated for solid pellet structure characterization, avoiding surface contamination.

Main Results:

• Analytical data confirmed the chemical stability of omeprazole pellets, with over 99.5% recovered.
• The addition of an alkalinizing excipient effectively neutralized the acidic effects of the enteric coating dispersion.
• Fluorescence imaging revealed no discernible in situ layer formation at the coat-core interface.

Conclusions:

• Fluorescence microscopy is a valuable tool for evaluating enteric coating integrity and stability.
• Incorporating basic excipients in the core or drug layer effectively manages microenvironmental pH, preventing coat-core interactions.
• The developed fracturing technique provides a reliable method for analyzing pellet structure without surface contamination.