Biological Availability of Ophthalmic Preparations. I. Increased Penetrability of theActive Ingredient Through the Cornea

Overview

Most eye diseases are treated by topical administration of ophthalmic preparations. Low ophthalmicbioavailability is due to a number of physiological and physicochemical factors. The main obstacleto the penetration of active ingredients to the eye is the layered character of the cornea. Formulationof ophthalmic preparations enabling easier penetration of this biological barrier thus ranks amongthe most effective ways of improving bioavailability. Penetrability of the cornea can be increased bythe following methods: a) adjustment of the actual acidity in such a way that pH of the preparationmakes it possible to produce the optimal portion of non-ionized particles; b) incorporation ofabsorption enhancers (non-ionic tensides, salts of bile acids, some antimicrobial substances, EDTA,cyclodextrins, etc.) into the composition of the preparation, and c) production of prodrugs or ionicpairs.

Key words:
ophthalmic preparations – biological availability – actual acidity –absorption enhancers – prodrugs – ion pairs