The processing and formulation (dosage form) of a drug may affect important pharmaceutical properties, such as form purity (whether the drug contains polymorphic or amorphous content, which might make it less therapeutically active), dissolution characteristics, chemical and physical stability, and bioavailability. Although it currently is not widely used for the characterization of pharmaceutical formulations, solid-state nuclear magnetic resonance (NMR) spectroscopy is a powerful technique that is useful for studying pharmaceutical materials. Because the spectrum for each polymorphic/amorphous form is often unique, the NMR method makes it possible to identify the state of the drug as well as the inactive ingredients used in drugs (excipients). Peaks from excipients are usually in a different region (chemical shift or frequency) of the NMR spectrum than are the peaks from drugs.