Understanding the impact of spray drying temperature on the dissolution behavior of a HPMC-AS spray dried formulation.

, the raisin-like particles and the hollow sphere particles from the same batch of SDD were physically separated by density for dissolution study. The separated hollow sphere SDD particles showed slower dissolution compared to the raisin-like SDD particles in both SDD powder form and drug product tablet form. Additional physical characterization and surface analysis were conducted on the SDD materials to understand the mechanism of the dissolution rate difference. Surface composition analysis by x-ray photoelectron spectroscopy (XPS) suggested that a higher concentration of the drug substance was present at the surface of the hollow sphere SDD particles than raisin-like particles. It is possible that the higher concentration of the poor soluble API on the surface of hollow sphere SDD particles resulted in more hydrophobic surface which led to slower dissolution rate.