Ocular drug delivery systems: A review

Abstract

The unique ocular route of drug administration comes with its own challenges, as novel nanotechnology based drug delivery systems and implants are being developed in order to overcome the drawbacks associated with conventional methods. Although, eye drops are convenient, safe, immediately active, patient compliant and non-invasive, the drug must be transported across several barriers, as most of the topically administered dose is lost rapidly within five to six minutes after administration due to reflux blinking and nasolacrimal drainage. Devices such as punctual plugs are used to prolong the retention time and increase the absorption of eye-drops, by blocking the nasolacrimal drainage system. Drug loaded nanoparticles have been developed in order to increase drug retention time, permeation and ocular bioavailability and intravitreal implants provide localized, controlled and sustained drug release over an extended period of time, with reduced side effects and enhanced ability to circumvent the blood retina barrier.