The Convenient Concentrating Method of Triamcinolone Acetonide for Intravitreal Injection and the Change of Intravitreal Concentration According to Initial Dosage

초록

Purpose: The most of clinicians have injected triamcinolone acetonide(TA) empirically with a concentration of 4mg/0.1ml. But it is difficult to inject high concentration with small volume due to inaccurate concentration method. So we tried to find out more convenient and accurate concentrating method. Furthermore we estimated the changes of intravitreal concentration after various initial injection dose and suggest possibility for the clinical use. Methods: The TA in a vial(40mg/ml) was shaken well and the whole volume of TA in a vial is lodged in 1ml tuberculin syringe. The tuberculin syringe was set up with needle-up position for 10,15,20,30, and 40 minutes so that crystals of TA could be sunken well. And the upper 0.9ml has been discarded. The rest 0.1ml of TA was measured by HPLC. 4, 8, 12, 16mg/ml of concentrated TA were injected into 48 rabbit eyes to measure intravitreal change of concentration. In the time interval of 1, 7, 14, 28 days, the vitreous body was obtained through enucleation and prepared for HPLC analysis. The TA concentration was identified and quantified by the HPLC and the fluorescence detector. Results: The average concentrations of TA obtained from the syringe with needle-up position were an 10.2 mg for 5 minutes, 14.9 mg for 10 minutes, 16.2 mg for 15 minutes, 17.5 mg for 20 minutes, 19.2 mg for 30 minutes, and 20.1 mg for 40 minutes per 0.1ml. In the concentration of 8mg/ml, intravitreal TA was decreased 1.59 times more slowly than in 4mg/ml. In the case of 12mg/ml, 2.15 times and in 16mg/ml, intravitreal TA was decreased 2.88 times more slowly than in 4mg/ml. Conclusions: We could figure out convenient concentrating methods available for clinical use of intravitreal TA. The decreasing rate of the intravitreal TA concentration has been reduced in proportion as initial concentration increases. With this result, we might predict effective duration of action of IVT according to initial concentration.