Improving the efficiency of existing drugs is currently one of the major goals of pharmaceutical industries. Rather than developing new drugs, which requires new clinical trials, the strategy is to improve the already tried-and-tested therapies. One of the characteristics with great ceiling for improvement is hydrophilicity; approximately 40% of approved drugs and nearly 90% of drugs under development are poorly water soluble, which leads to low bioavailability. In this sense, deep eutectic solvents comprising active pharmaceutical ingredients (API-DES) have emerged as alternative media capable of solubilizing poorly soluble compounds and enhance their bioavailability. In this proposal, inelastic neutron scattering (INS) will be applied to unravel the API-DES-Water interactions at a molecular level,