Ocular penetration enhancers drug delivery

J. Liaw and J.R. Robinson, Ocular penetration enhancers, in "Ophthalmic Drug Delivery systems",... 

This section will focus on the evolution and latest advancements of electrically assisted drug delivery as a tool for enhanced ocular drug penetration. A detailed review of different aspects of ocular iontophoresis can be found in Chapter 26. 

In addition to the use of penetration enhancers in eye solutions, both for improving the corneal and the conjunctival (systemic) delivery of drugs, the use of these agents has also been extended to their incorporation into other ocular delivery systems. For example, solid ocular inserts made of polyvinylalcohol (PVA) containing sulfadicramide and some absorption promoters, e.g., polyoxyethylene-9-lauryl ether, L-(lysophosphatidylocholine), and deoxy-cholic acid sodium salt, have been reported. Such inserts showed an increase in the penetration of the drug through the animal cornea in in vitro studies [108]. 

Kaur, I. P., and Smitha, R. Penetration enhancers and ocular bioadhesives Two new avenues for ophthalmic drug delivery. Drug. Dev. Ind. Pharm. 28(4) 353—369, 2002. 

Mucoadhesive Polymers as the Penetration Enhancers in Ocular Drug Delivery... 

The conventional concentration of benzalkonium chloride in eyedrops is 0.01%, with a range of 0.004-0.02% [111]. While uptake of benzalkonium chloride itself into ocular tissues is limited [113], even lower concentrations of benzalkonium chloride have been reported to enhance corneal penetration of other compounds including therapeutic agents [93,112,114]. The differential effect of this preservative on the cornea compared to the conjunctiva can be exploited to target a drug for corneal absorption and delivery to the posterior segment of the eye [115]. Its use has been proposed as a means of delivering systemic doses by an ocular route of administration [116]. 

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