Ocular Concentration after Subtenon and Intravitreal Injection of Triamcinolone Acetonide in Rabbits

Abstract

Purpose: To improve our understanding of the pharmacokinetics of triamcinolone acetonide (TA) and TA concentration in ocular tissue, TA concentration was measured in ocular tissue after intravitreal and subtenon injection. Methods: Fifteen rabbit eyes underwent subtenon TA injection (40 mg/1 ml), and another 15 rabbit eyes underwent intravitreal TA (4 mg/0.1 ml) injection. All eyes were enucleated at 1, 2, 4, 8, and 12 weeks after subtenon and intravitreal injection, and TA concentration in the aqueous and vitreous humor and the retina-choroid were measured by high performance liquid chromatography (HPLC). Results: In cases of subtenon's TA injection, TA concentrations were 0 ng/ml, 136.7 ng/ml, 178.7 ng/ml, 0 ng/ml, and 0 ng/ml in the aqueous humor; 99.1 ng/ml, 125.7 ng/ml, 726.8 ng/ml, 0 ng/ml, and 0 ng/ml in the vitreous humor; 72.7 ng/ml, 304.6 ng/ml, 459.0 ng/ml, 0 ng/ml, and 0 ng/ml in the retina-choroid after 1, 2, 4, 8, and 12 weeks, respectively. In cases of intravitreal TA injection, the measured values were 0 ng/ml, 0 ng/ml, 0 ng/ml, 654.1 ng/ml, and 0 ng/ml in the aqueous humor; 28152.2 ng/ml, 13646.4 ng/ml, 11388.8 ng/ml, 10297.2 ng/ml, and 183.0 ng/ml in the vitreous humor; and 0 ng/ml, 27.9 ng/ml, 108.3 ng/ml, 0 ng/ml, and 0 ng/ml in the retina-choroid at each time point. Conclusions: Intravitreal TA injection may be more effective for drug delivery than subtenon TA injection, but subtenon TA injection seems to be an effective and safe technique.