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 c arboxymethylcellulose (CMC) were used as a model beta-blocker and a viscous polymer, respectively. After intracapsular, retrobulbar and palpebral conj unctival injections (50 mu l) of tilisolol with 3% CMC into rabbits, drug c oncentrations in the tear fluid, blood, aqueous humor and vitreous body wer e determined by HPLC, Periocular injection (50 mu l) of tilisolol with 3% C MC showed slight leakage of the drug in the tear fluid from the injection s ite. 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 d rug at bath the injection site and in periocular tissues. Although the peri ocular injections with viscous vehicle (3% CMC) showed lower AUC in the aqu eous humor than that observed in instillation, they showed comparable AUC i n the vitreous humor. Compared to the results after the periocular injectio ns with buffer solution, CMC increased the AUCs in the vitreous body 3.1-fo ld with retrobulbar injection and 1.4-fold with palpebral conjunctival inje ction, 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.