DRUG-RELEASE FROM AN OPHTHALMIC INSERT OF A BETA-BLOCKER AS AN OCULAR DRUG-DELIVERY SYSTEM

Disc type ophthalmic inserts of beta-blockers were prepared with various polymers and drug release from the inserts were investigated. Tilisolol and poly(2-hydroxypropyl methacrylate) (HPM) were mainly used as models of beta-blocker and polymer for an ophthalmic insert. Release of tilisolol from ten different types of polymer inserts showed a variety patterns. In the inserts prepared with HPM and poly(2-hydroxyethyl methacrylate), the release data were fitted to a simple power equation and it was found that the release characteristics of tilisolol from these systems followed behavior conforming to a non-Fickian mechanism. The release of tilisolol from an HPM insert was examined under various conditions. Medium pH and medium temperature influenced the release of tilisolol from the HPM insert. Release of tilisolol from the HPM insert was not affected by drug load but by the amount of HPM. Various beta-blockers also showed controlled release from their HPM inserts. Macromolecular dye and insulin showed a slow release with an initial burst effect. Release data for an HPM insert under various conditions were also fitted to a simple power equation. The in vivo release pattern of tilisolol from an HPM insert in rabbit conjunctival sac reflected the in vitro release pattern. The constant releasing rate of tilisolol in the precorneal area was observed after application of the HPM insert of tilisolol in the puncta plugged rabbit. These results indicate that the polymer inserts can control drug release and might improve ocular bioavailability and reduce toxicity of ophthalmic drugs.