“…APIs have been found to exist in the solid state as polymorphs (Perlovich et al, 2012), amorphous solids (Dengale et al, 2014;Wlodarski et al, 2014), hydrates (Braun et al, 2013), solvates (Perlovich et al, 2012), coordination compounds (Yao et al, 2014), inclusion compounds (Sinha et al, 2005), salts (Hasa et al, 2013) and co-crystals (Aitipamula et al, 2013), which were capable of adjusting the physicochemical properties of APIs. In these solid states, the formation of salts due to their ability to readily alter the solubility and enhance the stability of APIs is usually given priority during the modification of ionizable APIs (Ong et al, 2012;Goud et al, 2013).…”