Deep eutectic solvents (DESs) are a new class of solvents that are nontoxic, low-cost, easy to prepare, tunable, and biodegradable. Their biocompatible properties enhance the efficacy of active pharmaceutical ingredients (APIs), opening up new possibilities for drug delivery. Moreover, DES can help in mitigating issues such as polymorphism or degradation, which pose challenges in drug formulation. DESs have the potential to become a universal drug delivery system due to their compatibility with proteins, flavonoids, nanoparticles, polymers, and surfactants. Furthermore, it is crucial to emphasize the advantages of DESs in pharmaceutical administration, such as improvement in drug solubilization, drug delivery pathways, and enhancing biological response toward several diseases. DESs are an innovative approach in pharmaceutical formulation and various routes of drug administration, which will be comprehensively covered in this chapter, along with the main challenges and limitations encountered with DESs in the pharmaceutical field.