Deep eutectic solvents comprising active pharmaceutical ingredients in the development of drug delivery systems

Introduction: Deep eutectic solvents comprising or acting as solvents of active pharmaceutical ingredients (API-DES) emerged as promising alternatives to improve therapeutic efficiency, with the additional possibility to integrate them in (bio)polymer-based systems to enhance their delivery. Areas covered: A critical review of the API-DES field evolution is herein presented, namely on the capacity of DES to integrate APIs in their composition and on the use of DES as solvents for APIs. These strategies avoid a current major concern related to drugs and APIs, i.e. polymorphism, and increase the solubility and bioavailability of the target API which leads to increased bioavailability. Owing to their composition versatility, polymerizable API-DES can also be prepared. Finally, the incorporation of API-DES in (bio)polymer-based systems to improve drug delivery is presented and discussed. Expert opinion: The relatively easy preparation of API-DES and their capacity to tune the API's release profile when incorporated in (bio)polymer-based systems represent an effective alternative to improve the APIs therapeutic action and to develop controlled drug delivery systems. Given the potential and progress demonstrated so far, the authors foresee further research on novel API-DES and on their delivery routes, envisaging the development of alternative therapies and final approval as therapeutics.