Ionic liquids: Future solvents and reagents for pharmaceuticals

The pharmaceutical industries are undoubtedly experiencing a series of challenges. One of these is the administration of solid form of many drugs due to many well known drawbacks including low solubility, polymorphic conversion and low bioavailability. Such problems are further aggravated when drug molecules or starting materials for synthesis of drugs are insoluble or sparingly soluble in aqueous media and most of pharmaceutical acceptable organic solvents. To overcome these problems, some times, highly polar organic solvents including pyridine, dimethylformamide (DMF) and N-methylpyrrolidone (NMP) which are not considered as environmental benign solvents have been used. These restrictions demand superior solvent systems and/or new drug forms that can be used as reaction media to avoid volatile organic solvents and/or as new forms of drugs. Much effort is being invested in such approaches to find new delivery technologies or development of new controlled-release dosage forms. In recent years, ionic liquids (ILs) that are salts of low melting point and consist only of ions have been increasingly exploited as solvents and/or (co)solvents and/or reagents in a wide range of pharmaceutical applications due to their tailor-made chemical, physical and biological properties. Studies have shown that ionic liquid-assisted drug carrier or active pharmaceutical ingredients (APIs) synthesized as IL form or many drug compounds produced using ILs as reaction media provide many unique and attractive properties compared to conventional counterparts. Furthermore, ILs could be employed as potential antimicrobial agents for various microorganisms. The aim of this article is to summarize the efforts placed on using ionic liquids in pharmaceutical applications.