Advanced Formulation Approaches for Ocular Drug Delivery: State-Of-The-Art and Recent Patents

Abstract

The eye presents extensive perspectives and challenges for drug delivery, mainly because of the extraordinary capacity, intrinsic to this path, for drugs to permeate into the main circulatory system and also for the restrictions of the ocular barriers. Depending on the target segment of the eye, anterior or posterior, the specifications are different. The ocular route experienced in the last decades a lot of progresses related with the development of new drugs, improved formulations, specific-designed delivery and even new routes to administer a drug. Concomitantly, new categories of materials were developed and adapted to encapsulate drugs. With such advances, a multiplicity of parameters became possible to be optimized as the increase in bioavailability and decreased toxic effects of medicines. Also, the formulations were capable to easily adhere to specific tissues, increase the duration of the therapeutic effect and even target the delivery of the treatment. The ascending of new delivery systems for ocular targeting is a current focus, mainly because of the capacity to extend the normal time during which the drug exerts its therapeutic effect and, so, supplying the patients with a product which gives them fewer side effects, fewer number of applications and even more effective outcomes to their pathologies, surpassing the traditionally-used eye drops. Depending on the systems, some are capable of increasing the duration of the drug action as gels, emulsions, prodrugs, liposomes, and ocular inserts with hydrophilic properties, improving the absorption by the cornea. In parallel, other devices use as a strategy the capacity to sustain the release of the carried drugs by means of erodible and non-erodible matrices. This review discusses the different types of advanced formulations used for ocular delivery of therapeutics presenting the most recent patents according to the clinical applications.

Advances in chemistry and composition of soft materials for drug releasing contact lenses

“…8,9 Due to difference in morphologies and barrier properties of the anterior and posterior segments in eye, different therapeutic measures have to be devised to ensure successful therapy. The anterior ophthalmic disorders are mostly treated with topical eye drops, whereas posterior segment disorders require many of the new methods including dendrimers, microneedles, 10 nanocrystals and lipid based nanosystems. 11 Nanotechnology can be used into various drug delivery systems to increase specicity and decrease off target toxicity.…”

Hydrogel Biomaterials for Application in Ocular Drug Delivery

“…The eye is composed of two segments; the anterior segment (composed of the aqueous humor, conjunctiva, cornea, iris, ciliary body, and lens) and the posterior segment (composed of the choroid, optic nerve, retina, sclera, choroid, and vitreous humor). Each segment is susceptible to a range of conditions and each poses its own challenges when it comes to drug delivery (Souto et al, 2019). There are two blood-ocular barriers; the blood-aqueous barrier and the blood-retinal barrier.…”

Noble Metals and Soft Bio-Inspired Nanoparticles in Retinal Diseases Treatment: A Perspective

“…Ocular transporters are divided in two groups: the solute carrier (SLC) family and the ATP-binding cassette (ABC) family. The electrochemical gradient was used by SLC transporters to induce the uptake of molecules through cell membrane, whereas ABC transporters employ ATP [21]. However, physiological eye phenomena, such as tear turnover, reflex blinking, ocular static, or lacrimal drainage reduce the action of the drug and consequently the eye drop administration fails to treat retina disease [22].…”