Two Contrasting Failure Modes of Enteric Coated Beads

Area of Science:

• Pharmaceutical Sciences
• Materials Science
• Physical Chemistry

Background:

• Enteric coatings protect drugs from stomach acid but can fail under storage conditions.
• Understanding coating failure mechanisms is vital for ensuring drug product stability and efficacy.

Purpose of the Study:

• To investigate the mechanisms and kinetics of enteric coated bead failure under high humidity and varying temperatures.
• To identify distinct failure models for enteric coated dosage forms.

Main Methods:

• Enteric coated beads were exposed to high humidity (75-98% RH) at temperatures ranging from 5-40°C.
• Analyses included acid dissolution, water activity, Scanning Electron Microscopy (SEM), X-ray Computed Tomography (X-ray CT), and Dynamic Mechanical Analysis (DMA).

Main Results:

• High humidity exposure led to increased drug release, failing dissolution specifications.
• SEM revealed cracks at 5°C and agglomeration at 40°C.
• X-ray CT showed core swelling and crack propagation; DMA indicated reduced glass transition temperature (T_g) of the coating.

Conclusions:

• Two distinct failure models were identified: core swelling-induced fracture at low temperatures and coating melt flow-induced agglomeration at higher temperatures.
• These findings provide critical insights into enteric coating stability and degradation pathways.