Abstract
Eyesight is one of the most well-deserved blessings, amid all the five senses in the human body. It captures the raw signals from the outside world to create detailed visual images, granting the ability to witness and gain knowledge about the world. Eyes are exposed directly to the external environment; they are susceptible to the vicissitudes of diseases. The World Health Organization has predicted that the number of individuals affected by eye diseases will rise enormously in the next decades. However, the physical barriers of the eyes and the problems associated with conventional ocular formulations are significant challenges in ophthalmic drug development. This has generated the demand for a sustained ocular drug delivery system, which serves to deliver effective drug concentration at a reduced frequency for consistent therapeutic effect and better patient treatment adherence. Recent advancement in pharmaceutical dosage design has demonstrated that a stimuli-responsive in situ gel system exhibits the favorable characteristics for providing sustained ocular drug delivery and enhanced ocular bioavailability. Stimuli-responsive in situ gels undergo a phase transition (solution–gelation) in response to the ocular environmental temperature, pH, and ions. These stimuli transform the formulation into a gel at the cul de sac to overcome the shortcomings of conventional eye drops, such as rapid nasolacrimal drainage and short contact time with the ocular surface This review highlights the recent successful research outcomes of stimuli-responsive in situ gelling systems in treating in vivo models with glaucoma and various ocular infections. Additionally, it also presents the mechanism, recent development, and safety considerations of stimuli-sensitive in situ gel as the potential sustained ocular delivery system for treating common eye disorders.
Highlights
Worldwide, eye disorders and consequential visual impairment are recognized as the nation’s absolute menace, compromising physical and mental health [1]
This can be reinforced by the in vivo pharmacodynamics study in glaucomatous rabbits’ model where it was demonstrated that the timolol maleate (TM)-loaded in situ gel possessed a more significant IOP-lowering effect compared to TM eye drops [27]
The main goal of advancing ocular drug delivery is to overcome the problems encountered with conventional drug delivery systems currently available in the market. pH-responsive in situ gelling systems integrate polymers that are capable of responding to the external pH environment, transforming from a solution to a gel matrix
Summary
Eye disorders and consequential visual impairment are recognized as the nation’s absolute menace, compromising physical and mental health [1]. Metabolic barriers involve efflux pumps or enzymes that may deactivate drugs These factors lead to accelerated precorneal drug clearance, low ocular contact time, and limited drug ocular bioavailability (
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