Solid-State Nuclear Magnetic Resonance in Pharmaceutical Compounds

The solid-state characterization of novel pharmaceutical compounds remains an important issue. Solid-state NMR is one of the techniques of choice to gain information when other techniques are not available. Knowledge of the molecular structure in the solid state can lead to better design and control the behaviour of the drug as it affects important properties such as solubility in aqueous medium. Many different NMR experiments can be performed to obtain either structural or dynamic information on very broad space and time ranges, respectively. Contrary to others techniques, not only crystalline material but also amorphous materials can be studied by SSNMR. These and other aspects make SSNMR a very powerful technique to obtain relevant information on solids pharmaceutical forms. We will discuss the SSNMR most common experiments used to investigate pharmaceutical compounds, including one-and two-dimensional experiments and relaxation time measurements. Additionally, we will mention some aspects of first principle calculation. Also we highlight the importance of NMR as a multinuclear technique. We will focus on SSNMR applied for characterization of new developed active pharmaceutical compounds and formulated drugs. We will pay attention to some particular topics as polymorphism, complexes with cyclodextrin and an emerging issue in pharmaceutical industry as it is the development of cocrystals. NMR crystallography is also discussed.