Solid-state NMR studies of pharmaceutical systems

High- and low-resolution solid-state nuclear magnetic resonance (SSNMR) applications to the study of pharmaceuticals are reviewed. Examples are shown involving the use of mono- and bidimensional SSNMR techniques based on different nuclear interactions and the measurement of several nuclear parameters, such as chemical shifts, line widths, and relaxation times (T1, T2, T1r). The systems investi- gated include pure active pharmaceutical ingredients (APIs), substances used as drug excipients, and solid dispersions formed by APIs and excipients, up to final drug formulations. The most important aspects treated concern structural, dynamic, and morphological properties, and, in particular, identification, characterization, and quan- titation of polymorphs and related forms, conformational and crystalline packing behavior, amorphous phase properties and stability, effects of drug processing, molecular motions, API-excipient and excipient-excipient chemical and physical inter- actions, and phase mixing in heterophasic systems.