Investigation of Polymorphism and Cocrystallization of Active Pharmaceutical Ingredients Using Vibrational Spectroscopic Techniques

Active pharmaceutical ingredients (APIs) can exist in various types of crystalline forms including polymorphs and cocrystals. These multiple crystalline forms of APIs have district physical and physicochemical characteristics. Vibrational spectroscopic techniques used in solid-state pharmaceutical analysis include mid-infrared, Raman and terahertz spectroscopy. In this review, we will focus on the recent vibrational spectroscopic investigation on the polymorphism and cocrystallization of APIs in pharmaceutical fields. The distinctive spectral and structural information of pharmaceutical polymorphs and cocrystals could be obtained based on these vibrational spectroscopic techniques. Keywords: Polymorphism, cocrystallization, vibrational spectroscopy, mid-infrared spectroscopy, Raman spectroscopy, terahertz timedomain spectroscopy, active pharmaceutical ingredients.