Enteric Microcapsules Encapsulation of Roxithromycin-PVP Composite Core Particles to Inhibit Drug Crystallization upon Fluidized Bed Method for Oral Administration

Enteric-coated microcapsules can protect roxithromycin (ROX) from acid hydrolysis enhancing efficacy, solubility, and dissolution rate, representing a promising oral formulation for children and patients with swallowing difficulties. ROX-layered core particles were obtained with polyvinylpyrrolidone (PVP) K30 as the binder and Eudragit L30 D-55 as the coating material using the Wurster process in a fluidized bed processor. The enteric-coated microcapsules were characterized using powder X-ray diffraction, differential scanning calorimetry, and polarized optical microscopy. Enteric microcapsules with appropriate coating levels and particle sizes underwent dissolution tests, acid resistance tests. The weight ratio of PVP K30 to ROX was 1/2, and the average particle size of ROX-layered core particles was 130 µm. ROX molecule crystallinity in the layered core particles was inhibited. ROX was dispersed in PVP K30 with small particle size and high wettability. The average particle size of ROX enteric microcapsules with 60% coating level was approximately 155 µm. The acid resistance test showed that enteric microcapsules with a coating level of >50% and plasticizer contents of 20-25% can effectively protect ROX stability in simulated gastric fluid within 2 h. The dissolution experiment showed that the enteric microcapsules could protect ROX under acidic conditions of pH 1.2 and released >75% of ROX in the simulated intestinal fluid at pH 6.8 in 45 min. The enteric microcapsule of ROX using Wurster fluidized bed method can protect ROX from acid hydrolysis to ensure the efficacy, and has potential application in pharmaceutical industries, owing to its favorable dissolution.