Ocular drug delivery system: Challenges and approaches

Abstract

The ocular drug delivery deviates through a number of anatomical and physiological barriers, which have been a bottleneck for the ophthalmologists. The ocular barriers, static and dynamic, decrease the absorption of the therapeutic agents and the entry of the xenobiotics. Thus, a conventional ocular dosage form has various disadvantages of its use in ocular diseases. Hence, an ideal ocular delivery system has always been aimed, where the bioavailability of a drug is maintained for a longer period of time. The present review aims to focus on the drawbacks of the conventional ocular therapy and the advantages of designing novel delivery systems, with their certain specific advantages in ocular pharmacokinetics and the enhancement of bioavailability. These novel approaches emphasize on the benefits of various ocular drug delivery systems, like eye ointments, gels and use of viscosity enhancers, prodrugs, penetration enhancers, microparticles, liposomes, niosomes, ocular inserts, implants, intravitreal injections, nanoparticles, nanosuspension, microemulsion, dendrimers, in situ gels, iontophoresis and periocular injections. The compiled data presented in this review will act as a good information resource and reference point for further researches in the field of ocular drug delivery aiming non-invasive sustained release of drugs in the anterior and posterior segments of the eye.