Deep eutectic solvents formed by pharmaceutical ingredients and their potential influences on solid preparations

Some active pharmaceutical ingredients (APIs) and excipients can form deep eutectic solvents (DESs), which will lead to severe defects in solid preparations. This work first prepared related typical DESs by mixing APIs and excipients from marketable drugs. Then two different types of the binary eutectic mixtures were investigated, which were composed of menthol (HBD) and citric acid (HBA) (ME/CA) as well as phenyl salicylate (HBA) and benzoic acid (HBD) (Salol/BA). These binary mixtrures were applied to investigate their possible effects on capsules and tablets, which could be liquefaction or the stickiness of the solid formulations. The comprehensive characterizations and studies on phase behaviors of the binary mixtures were carried out, and the spectral analysis confirmed the formation of the eutectic liquids from individual components. Furthermore, the binary mixtures have increased the tablet strength when increasing the compression force, leading to the stickiness of powders during pressing. Moreover, the capsules were softened by the existence of DESs. After morphological observation and quantitative analysis, the corresponding suggestions and countermeasures were provided in the conclusions.