Enhancing Microemulsion based Therapeutic Drug Delivery: Exploring Surfactants, Co-surfactants, and Quality by Design Strategies within Pseudo-ternary Phase Diagrams

Microemulsions are thermodynamically stable, clear and homogeneous mixtures of oil, water, and surfactants that have garnered significant attention in various industrial and biomedical applications. The basic components of microemulsions are oil, water, and surfactant, and their composition ratios play a crucial role in determining their properties and stability. Factors such as the type of surfactant, oil, and water used, temperature, and the presence of cosurfactants can greatly influence the formation, stability and properties of microemulsions. These are appropriate for use in drug delivery applications because to their physicochemical characteristics, which include small droplet size, large interfacial area, and good solubilization capacity for both hydrophilic and hydrophobic drugs with significant improvement in their biological activity. The theories of microemulsion and the role of phase diagrams in microemulsion formation and various components for choice of surfactant and co-surfactant are explained. Recent advancements in the preparation and characterization techniques of microemulsion, ranging from visual inspection to the phase behaviour studies and advanced spectroscopic techniques, with a focus on potential of microemulsion in drug delivery along with microemulsion-based drug candidates that are most commonly used for its formulation are also discussed. The review helps in understanding how different excipients affect the release of the active pharmaceutical ingredient. The quality by design approach utilized for optimization of microemulsions is also discussed.