Innovative Preservative-Free Ophthalmic Drug Delivery Systems: Current Advances, Challenges, And Future Perspectives-A Review

Abstract

Ocular drug delivery remains a formidable challenge in pharmaceutical science due to the eye's specialized anatomical and physiological defense mechanisms, including rapid tear turnover, blinking reflexes, precorneal drainage, and protective tissue barriers. Conventional eye drops typically suffer from extremely low ocular bioavailability (often less than 5%) and require frequent administration, frequently leading to poor patient compliance. Furthermore, conventional multi-dose formulations routinely rely on chemical preservatives (such as benzalkonium chloride) to prevent microbial contamination. Long-term exposure to these preservatives is well-documented to induce ocular surface toxicity, tear film instability, goblet cell loss, and exacerbated inflammation, particularly in chronic conditions like dry eye disease and glaucoma. In response to these clinical limitations, recent pharmaceutical engineering has shifted toward innovative, preservative-free ophthalmic drug delivery systems (PF-ODDS). This review highlights current technological breakthroughs—such as advanced nanocarriers (nanoparticles, liposomes, nanoemulsions, and nanomicelles), stimuli-responsive in situ hydrogels, contact lens-mediated delivery, and multi-dose preservative-free squeeze dispensers. Additionally, we examine the manufacturing and regulatory hurdles associated with sterile, preservative-free formulations, discuss strategies to enhance precorneal residence time and bioavailability, and outline future perspectives for targeted, patient-centric ocular therapeutics.