Deep eutectic solvents in pharmaceutical applications: A review

Deep eutectic solvents (DESs) have garnered significant attention in pharmaceutical research in recent years due to their high efficiency, facile separability and biocompatibility. Characterised by hydrogen-bond donors (HBDs) and hydrogen-bond acceptors (HBAs), DESs exhibit low toxicity, favourable biodegradability, and excellent solubilising properties, rendering them promising alternatives to conventional organic solvents in drug synthesis, natural active ingredient extraction and drug delivery. This review systematically evaluates the broad pharmaceutical applications of DESs, with particular emphasis on enhanced drug solubility and bioavailability. In plant extraction, DESs outperform traditional solvents (e.g., diethyl ether) by improving the recovery efficiency of bioactive compounds. In drug synthesis, certain DESs function simultaneously as reaction media and catalysts, enhancing reaction efficiency and selectivity while minimising environmental impact. In drug delivery, DESs facilitate transdermal and oral absorption through interactions with biological membranes, making improved delivery efficiency. Despite these advantages, challenges remain, including high viscosity, formulation complexity, and unresolved regulatory considerations. Future research must focus on physico-chemical optimisation, safety evaluation, and scalable production to fully realise the potential in pharmaceutical applications.