Ionic Liquids for Transdermal Drug Delivery: Choline Geranate System as a Case Study

Transdermal administration is of high interest for drug delivery due to its non-invasiveness and easy dosing. However, this route of drug delivery faces the challenges of low drug permeability across the skin. This chapter reviews the role of ionic liquids (ILs) for transdermal delivery of active pharmaceutical ingredients (APIs). In particular, it focuses on the case of the Choline Geranate (CAGE), including its synthesis, structural features, physical properties, and enhanced permeation across epithelial barriers as a transdermal drug carrier. Its scale-up and medical applications are also discussed. This system has potential to become a powerful excipient to improve the pharmacokinetic profiles of many pharmaceutical products in transdermal applications.