Asymmetry in Drug Permeability through the Cornea.

Nadia Toffoletto,Anuj Chauhan,Ana Paula Serro,Benilde Saramago,Carmen Alvarez-Lorenzo

doi:10.3390/pharmaceutics13050694

Abstract

The permeability through the cornea determines the ability of a drug or any topically applied compound to cross the tissue and reach the intraocular area. Most of the permeability values found in the literature are obtained considering topical drug formulations, and therefore, refer to the drug permeability inward the eye. However, due to the asymmetry of the corneal tissue, outward drug permeability constitutes a more meaningful parameter when dealing with intraocular drug-delivery systems (i.e., drug-loaded intraocular lenses, intraocular implants or injections). Herein, the permeability coefficients of two commonly administered anti-inflammatory drugs (i.e., bromfenac sodium and dexamethasone sodium) were determined ex vivo using Franz diffusion cells and porcine corneas in both inward and outward configurations. A significantly higher drug accumulation in the cornea was detected in the outward direction, which is consistent with the different characteristics of the corneal layers. Coherently, a higher permeability coefficient was obtained for bromfenac sodium in the outward direction, but no differences were detected for dexamethasone sodium in the two directions. Drug accumulation in the cornea can prolong the therapeutic effect of intraocular drug-release systems.

Highlights

The eye structure is endowed with efficient protective barriers and mechanisms, which constitute a challenging obstacle to ophthalmic drug delivery [1]
The experiments were performed with single- and dual-drug solutions to investigate whether the concomitant presence of both drugs may have any effect on the permeability solution was observed for bromfenac in the the cornea inwardare direction; of drug each drug
Permeability tests evidenced a higher drug accumulation in the cornea when the drug solution is applied in an outward corneal configuration

Summary

Introduction

The eye structure is endowed with efficient protective barriers and mechanisms, which constitute a challenging obstacle to ophthalmic drug delivery [1]. The efficiency of drug administration through eye drops is limited by several factors, including low corneal permeability, drug loss with lacrimation and scarce patient compliance to the treatment, especially when elderly patients are involved [2,3]. Progress has been made in the development of alternative drug delivery vehicles, namely drug-loaded contact lenses (CLs) and intraocular lenses (IOLs), able to sustain drug release over time in the cornea and in the anterior chamber, respectively [4,5,6]. Drug-loaded IOLs, in particular, could substitute the prophylaxis after cataract surgery in a patient-friendly and more efficient way, as they overcome the corneal barrier by delivering drugs directly inside the eye. The eventual accumulation of the drug released from the IOL in the cornea may constitute an advantage to treat both the anterior and posterior segments

Methods

Results

Discussion

Conclusion