Recent Advances in Ophthalmic Drug Delivery

Abstract

Publisher Summary In this chapter, the formulations, dosage forms, and delivery devices studied by the pharmaceutical industry and research institutions and the various approaches for designing tomorrow's ophthalmic products are provided. The eye presents unique challenges for drug delivery due to its anatomy and natural protective mechanisms. The constant tear turnover, drainage, and sensitivity to foreign bodies, as well as the low permeability of the cornea, results in low bioavailability of ophthalmic medications administered topically using conventional dosage forms such as eye drops. Ophthalmic drugs delivered via systemic routes have proven even less successful due to the blood–aqueous and blood–retinal barriers and significant side effects associated with systemic exposure to large doses of drugs. In recent years, research activities have increasingly focused on the periocular route. Indeed, given the corneal barrier to drug penetration, it seems logical to consider the conjunctival–scleral route as an alternative for delivering drugs to both the anterior and posterior segments of the eye, since the drug permeability in the sclera has been reported to be approximately 20 times greater compared to the cornea. Passive diffusion through an interfibrillar aqueous pathway is likely to be the primary mechanism of drug permeation across the sclera due to its high water content. For delivering drugs to the posterior segment of the eye, in particular, the trans-scleral route appears to be a promising alternative to the intravitreal route in light of the large scleral surface area, relatively few protein-binding sites, and its less invasive nature.