Drug delivery systems ocular inserts

An erodible insert developed as a potential ocular drug-delivery system is marketed as a prescription drug for the lubricant properties of the polymer base. Lacrisert is a sterile ophthalmic insert used in the treatment of moderate to severe dry eye syndrome and is usually recommended for patients unable to obtain symptomatic relief with artificial tear solutions. The insert is composed of 5 mg of hydroxypropylcellulose in a rod-shaped form about 1.27 mm diameter by about 3.5 mm long. No preservative is used, since it is essentially anhydrous. The quite rigid cellulose rod is placed in the lower conjunctival sac and first imbibes water from the tears and after several hours forms a... 

Sasaki, H.,Tei,C.,Nishida,K., and Nakamura, J. (1993), Drug release from an ophthalmic insert of a beta-blocker as an ocular drug delivery system, / Controlled Release, 27(2), 127-137. 

Ocular inserts serve as an alternative approach to overcome the problans that were faced by other ocular drug delivery systems. They represent a significant advancement in the therapy of eye disease. 

Bawa, R. Ocular inserts. In Mitra, A.K. (ed.) Ophthalmic Drug Delivery Systems, pp. 223-260. Dekker, New York (1993)... 

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]. 

Topically applied ophthalmic drugs are used for their local effects (see Chapter 63) requiring absorption of the drug through the cornea corneal infection or trauma thus may result in more rapid absorption. Ophthalmic delivery systems that provide prolonged duration of action (e.g., suspensions and ointments) are useful, as are ocular inserts providing continuous delivery of drug. 

Frequent instillation of solution or higher drug concentration is needed to achieve the desired therapeutic response. But this attempt is potentially dangerous if drug solution drained from the eye is systemically absorbed from the nasolacrimal duct. To increase precorneal residence time and ocular bioavailability, different ophthalmic delivery systems such as viscous solutions, ointments, gels, suspensions, or polymeric inserts are used. But because of blurred vision (e.g., ointments) or lack of patient compliance (e.g., inserts), these formulations have not been widely accepted. 

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