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M. Nozaki, K. Okabe, J. Okabe, Y. Ogura; Intraocular pharmacokinetics of triamcinolone acetonide after intravitreal and posterior sub–Tenon’s capsule injections . Invest. Ophthalmol. Vis. Sci. 2004;45(13):1920.
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Purpose: Intravitreal and posterior sub–Tenon’s capsule injections of triamcinolone acetonide (TA) have been reported to resolve macular edema and to improve the vision. We comparatively studied the intraocular pharmacokinetics of TA after intravitreal, posterior sub–Tenon’s capsule, and the simultaneous injections of the both routes. Methods: The pigment rabbits were first divided into 2 groups. Rabbits in the group A (n=48) were treated by the injection of TA without vitrectomy and rabbits in the group B (n=36) were received gas vitrectomy before the treatment. TA was administered in the 3 ways; 1) 4 mg–intravitreal injection, 2) 20 mg–posterior sub–Tenon’s capsule injection and 3) simultaneous administration of the both 4 mg–intravitreal injection and 20 mg–posterior sub–Tenon’s capsule injection ("sandwich" injection). Four rabbits each were sacrificed at the intervals ranging from one day to 8 weeks. The vitreous, retina–choroid and aqueous humor were sampled and processed for high–performance liquid chromatography (HPLC) analysis to determine the concentrations of TA. Results: In the non–vitrectomized eyes (group A), the concentrations of TA in the retina–choroid were higher in the "sandwich" injection group than in the intravitreal injection group at 8 weeks. Fifteen percent of TA was remained in the vitreous at 8 weeks in the intravitreal injection group and the "sandwich" injection group. In the vitrectomized eyes (group B), only 7 % of TA was remained in the both groups at 8 weeks. Conclusions: These results suggested that TA "sandwich" injection maintains higher concentrations in the retina–choroid than the intravitreal injection for the long period. Although the clearance of TA from the vitreous cavity was faster in the vitrectomized eyes, there was no significant difference between the non–vitrectomized and the vitrectomized eyes in the concentrations of retina–choroid with these doses of TA.
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