Topical delivery system of ophthalmic drugs by periocular injection with viscous solution

The purpose of this study is to evaluate periocular injections with viscous solution as a topical delivery system of ophthalmic drugs. Tilisolol and carboxymethylcellulose (CMC) were used as a model beta-blocker and a viscous polymer, respectively. After intracapsular, retrobulbar and palpebral conjunctival injections (50 microl) of tilisolol with 3% CMC into rabbits, drug concentrations in the tear fluid, blood, aqueous humor and vitreous body were determined by HPLC. Periocular injection (50 microl) of tilisolol with 3% CMC showed slight leakage of the drug in the tear fluid from the injection site. The viscous vehicle decreased the absorption rate constant of the drug from the injection site to systemic circulation compared with the buffer solution. It suggests that the viscous solution improved the retention of drug at both the injection site and in periocular tissues. Although the periocular injections with viscous vehicle (3% CMC) showed lower AUC in the aqueous humor than that observed in instillation, they showed comparable AUC in the vitreous humor. Compared to the results after the periocular injections with buffer solution, CMC increased the AUCs in the vitreous body 3.1-fold with retrobulbar injection and 1.4-fold with palpebral conjunctival injection, respectively. As a result, periocular injections with 3% CMC showed higher delivery of tilisolol to the vitreous body against the aqueous humor than the instillation and periocular injections with buffer solution.