Physicochemical Principles of Adsorption in Pharmaceutical Systems and Drug Delivery Applications

The phenomenon of adsorption is a basic physicochemical behavior that controls molecular interactions at the interfaces in pharmaceutical formulations. From a physicochemical point of view, it has an impact on drug–drug, drug–excipients or drug–carriers’ interactions and with the biological surfaces provoking effects such as enhanced loading efficiency of the drug to the delivery system, improved stability of formulations for topical applications (prevents substance migration), dissolution properties (bioavailability enhancement) and therapeutic efficacy. In the pharmaceutical industry, adsorption is connected with fundamental processes like controlled drug liberation, surface-mediated transport and interactions with proteins and cell membranes. Surface properties, molecular structure, thermodynamic driving forces and adsorption kinetics determine the reaction pathways. This review delivers a specific mechanistic overview of the mechanism of adsorption process in pharmaceutical systems by integrating physical chemical principles, and adsorption isotherms as well as the kinetic and thermodynamic models related to drug delivery. Special emphasis is given to adsorption-based delivery systems and adsorption occurring at biological interfaces, demonstrating how fine tuning of the adsorption process enables rational formulation design, increases therapeutic efficacy, and minimizes unwanted interactions.