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M. Higashiyama, A. Ohtori; Intraocular Concentration of Triamcinolone Acetonide After Sub–Tenon Injection . Invest. Ophthalmol. Vis. Sci. 2005;46(13):5393.
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Purpose: To explore for intraocular behavior of triamcinolone acetonide (TA) after sub–tenon injection. Methods: A 0.1 mL of 10% TA suspension was injected into sub–tenon capsule of right eye on albino rabbit. At 1, 6 hours, 1, 2, 7, 31, 62, 91 and 123 days after injection, 5 rabbits each were sacrificed and the aqueous humor was withdrawn. Both right and left eye were enucleated and observed the remains of drug macroscopically. Then the sclera, choroid, retina, vitreous body, lens and iris–ciliary body were collected. The sclera was divided into two pieces; the injected area (upper sclera) and untreated area (lower sclera). TA concentration in each tissue was determined by HPLC. Results: A cake of TA particles remained in sub–tenon capsule on right eye was observed macroscopically up to 62 days after injection. The maximum concentration in upper sclera, which was exposed to the drug, was observed at 1 hour after injection, and then the concentration gradually decreased with time. The concentration–time profiles in lower sclera, choroide, retina and vitreous body almost synchronized with that in upper sclera throughout the experiments. The lower sclera level was considerably lower than that in upper sclera. TA was not detected in untreated (left) eye at all. The finding suggested that a large amount of TA was reached to intraocular tissues directly from the sclera not through systemic circulation, and that the difference of concentration between the upper and lower sclera may cause a range of concentration in each intraocular tissue. TA was distributed as far as in aqueous humor and iris–ciliary body, the elimination from the anterior tissues was rather rapid unlike posterior tissues. The distribution to anterior tissues was assumed from the elimination to be transcorneal absorption of leakage drug. Conclusions: The sub–tenon injection makes it possible to reach a large amount of drug to posterior tissues by single administration. It may be applied to target treatment on limit area by positioning the drug adjacent to the disease, since the drug was mainly distributed in the injected area. However the elimination profile of posterior tissues suggested that the decrease of drug concentration in target tissues partly cause recurrence on clinical treatment of macular diseases.
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