(571h) Microstructure of Drug/Polymer Solid Dispersions

The purpose of this study is to understand the microstructure of drug/polymer solid dispersions. Mixtures of the model drug and polyethylene glycol (PEG) were melted and recrystallized at different temperatures. Small-angle x-ray scattering was used to investigate the location of drug in the polymeric carrier and make inferences about the size of the drug domains. The morphology of the drug-PEG dispersions was probed using Atomic Force Microscopy and optical microscopy. When chlorpropamide was mixed with the PEG carrier to form chlorpropamide/PEG dispersions, the diffraction peak in the small-angle X-ray scattering profile shifted to a smaller scattering vector, which corresponded to a larger long period. The increase of the long period, which is the sum of the thickness of the crystalline lamellae and amorphous phase of PEG, suggested that a portion of chlorpropamide may exist within the interlamellar regions of the PEG carrier. When preparing dispersions with aceclofenac, the long period once again increased, indicating the interlamellar aggregation of aceclofenac in the PEG carrier. In contrast, for dispersions of haloperidol/PEG, the diffraction peaks remained at the same positions, indicating that all the haloperidol had been excluded to the interfibrillar or interspherulitic regions in the carrier. The AFM images further verified the SAXS results.