Ionic liquids as transdermal drug carriers: A review of recent advancements

Ionic liquids (ILs) comprise organic cations and either inorganic or organic anions and exist in a liquid state at room temperature. Owing to their simple preparation, good stability, strong solubility, and adjustable structure, ILs have been widely explored in biomedicine. ILs increase the solubility and stability of insoluble drugs, are biocompatible, and promote transdermal drug penetration, rendering them potential carriers in transdermal drug delivery systems. In addition, they can form active pharmaceutical ingredient ILs, improve the bioavailability of drugs, enhance efficacy, and overcome current limitations in transdermal drug delivery systems. This review comprehensively evaluates the development history, classification, and design of ILs, focusing on their applications and safety. Moreover, it summarizes new IL-based drug delivery preparations and provides references for further research and development of ILs in transdermal drug delivery systems.