The Role of Surface Active Agents in Ophthalmic Drug Delivery: A Comprehensive Review

With the significant advances made in nanotechnology, research efforts focused on developing novel drug delivery platforms that can overcome the multitude of challenges encountered in ophthalmic drug delivery. Surface active agents (SAAs) have been extensively used for the formulation of many of the dosage forms targeting ocular tissues. Novel ophthalmic carriers utilizing SAAs were broadly classified into particulate, vesicular, and controlled release drug delivery systems. Depending on their physicochemical properties, SAAs can perform a variety of roles ranging from wetting agents, emulsifiers, stabilizers, charge inducers, solubilizers, antimicrobial agents, corneal permeation enhancers, and gelling agents. Nevertheless, their use is limited by their potential toxicity and possible interactions with other formulation ingredients. This review provides a comprehensive analysis of the different functional roles of SAAs in novel ophthalmic drug delivery platforms, their mechanism of action, and limitations that need to be considered during formulation to maximize their potential benefit. Understanding the mechanisms by which they perform their different roles and the possible interactions between SAAs and other formulation ingredients can help orientate the choice of formulators toward the SAA most suitable for the intended ocular application at a concentration that is both safe and effective.