Mid-Infrared Spectroscopy of Pharmaceutical Solids.

It is now well established that infrared absorption spectroscopy is a powerful technique for the physical characterization of pharmaceutical solids. Besides being a preferred methodology for identification purposes, one can use trends in the energy values in the spectra as a means to study the solid-state properties of the system. FTIR spectra are often used to evaluate the type of polymorphism existing in a drug substance, can be very useful in studies of the water contained within a hydrate species, and are emerging as a technique of choice for the study of cocrystal systems. In this review, an overview of the theoretical foundations for infrared spectroscopy will be presented, which will be supported by illustrations as to how the methodology can be used.