Change of Residual Period and Clearance Rate of Intravitreal Triamcinolone According to Initial Injection Dosage

Kim, Tae Hwan; Moon, Yeon Sung; Chin, Hee Seung

Abstract

PURPOSE
We sought to determine how the initial concentration of triamcinolone acetonide injected intravitreally might influence the clearance and residual period of the intravitreal triamcinolone acetonide. METHODS: Sixty-four eyes of 32 rabbits were divided into 4 groups. Each group was injected with 5, 10, 15, or 20 mg/0.1 ml of triamcinolone acetonide intravitreally. At 1, 7, 14, and 28 days after intravitreal injection, four eyes were obtained from each group by sacrificing two rabbits. The vitreous bodies were obtained and prepared for HPLC analysis. The concentrations of triamcinolone acetonide were quantitated by HPLC with fluorescence detector. We compared the data using the logarithmic regression coefficients of each line. RESULTS: The elimination half-lives of the intravitreal triamcinolone acetonide were 3.23 days, 3.73 days, 4.11 days, and 4.98 days at the initial injection doses of 5, 10, 15, and 20 mg per 0.1 ml, respectively. Compared to the 5 mg initial dose, the clearance rate of the intravitreal triamcinolone acetonide was decreased 1.15 times, 1.27 times and 1.55 times at 10 mg, 15 mg, and 20 mg of the initial dose, respectively. CONCLUSIONS: The residual duration of intravitreal triamcinolone acetonide was prolonged as the initial concentration of intravitreal injection increased. Furthermore, the clearance rate decreased as the injection dose is increased. This shows that higher injection doses of triamcinolone acetonide induce not only an increased intravitreal concentration, but also prolonged the duration of effectiveness.