Ionic Liquid-Enabled Drug Delivery Systems: Benefits, Limitations, and Future Perspectives

ILs have emerged as versatile formulation components in DDS due to their tunable physicochemical properties and ability to modulate biomolecular and interfacial interactions. This review examines IL-enabled DDS strategies across major delivery platforms, including nanocarrier-based systems, microtechnology-assisted devices, and biomacromolecule formulations, with emphasis on formulation design principles rather than administration route. We discuss how ILs enhance API solubility, stability, permeability, and formulation flexibility through API–IL complex formation and controlled membrane interactions and relate mechanistic insights into IL–membrane interactions to both delivery performance and safety via structure–activity relationships. Current limitations, including toxicity concerns, lack of standardized evaluation criteria, scalability challenges, and regulatory ambiguity, are critically assessed. Overall, this review positions ILs as formulation-enabling materials rather than standalone therapeutics and underscores the importance of rational design, standardized assessment, and early regulatory alignment for advancing IL-enabled DDS toward clinical translation.