Solid-state NMR spectroscopy can provide unique insight into the composition and properties of pharmaceutical formulations. In particular, both structural and mobility information can be obtained, but the challenge is to relate that information to functional properties such as physical and chemical stability, dissolution rate, and processing parameters. We will show how solid-state NMR spectroscopy is a powerful technique to study polymorphism, form changes upon processing, the presence of small amounts of amorphous drug in crystalline solids (for chemical/physical stability), and small amounts of crystalline drug in amorphous solid dispersions (for physical stability). In addition, we will show how solid-state NMR relaxation times can be used to measure particle size, crystal defects, and chemical impurities in crystalline materials, as well as determine phase separation in amorphous formulations. Finally, mobility, phase separation, and microenvironment acidity has been studied to predict stability in large-molecule formulations.
