Cross-Sectional Imaging of Coated Drug Granules

Abstract

Coatings on pharmaceutical products serve many purposes such as hiding an unpalatable drug taste, giving increased stability, and providing controlled-release dosage. The analysis of coatings on drug granules has been performed through “bulk” studies, such as dissolution tests, stability tests, and sieve analysis, which provide little direct structural information about the coating. Microstructural information such as coating thickness, uniformity, and porosity is necessary to help optimize processing conditions as well as to predict dissolution behavior and resultant biological activity. A sample preparation method is described which permits successful imaging of granule drug coatings without sampling bias. Information about the coating structure is obtained through morphometric analysis of cross sectioned embedded granules.The granules studied were prepared through a wet granulation process and contain approximately 13% (by weight) drug, 4% corn starch, and 83% sucrose. This inner granule (200-250 μm) was coated (10 μm) with an hydrogenated cotton seed oil in a spray congealing microencapsulating process.