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M.C. Wills, R.J. Munger, G. Baskin, S. Bussa, T. Hack; Intravitreal Triamcinolone Acetonide in Cynomolgus Monkeys: Results of a Toxicity Study . Invest. Ophthalmol. Vis. Sci. 2005;46(13):490.
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Purpose: The study examined the potential toxicity to the eye (in general) and to the retina (in particular) of triamcinolone acetonide (TA, Kenalog–40®), a corticosteroid anti–inflammatory agent, when administered by intravitreal injection to male cynomolgus monkeys every 4 weeks for 3 months. Methods: Six experimentally naive male cynomolgus monkeys received a 50 µL intravitreal injection of TA (2 mg/eye, 40 mg/mL) in the left eye on study days 1, 28, and 56. Right eyes received a 50µL injection of balanced salt solution as a control. The intravitreal dose level was based on the projected dose for clinical trials (100 µL, 4 mg TA) and was chosen with consideration to gross differences in relative ocular size and volume between cynomolgus monkeys and humans. Animals were evaluated for changes in clinical signs, body weight, food consumption, ocular condition, retinal conductivity, tonometry measurements and clinical pathology indices. All animals were euthanized approximately two weeks after the last dose. At termination, a full necropsy was conducted on all animals. Ocular–associated tissues_cornea, anterior chamber, lens, retina, ciliary body, iris, choroids, sclera, eyelid, lacrimal gland, optic nerve, and conjunctival mucosa_were examined histologically. Results: Intravitreal injections of TA (2 mg/eye) were well tolerated. There were no clinical signs that were clearly related to repeat injections. Examinations by biomicroscopy, indirect ophthalmoscopy, electroretinography and tonometry revealed no adverse effects from the 3 monthly injections of TA. Treated eyes compared favorably with those receiving injections of the balanced salt solution control. There were no TA–related changes in serum chemistry, hematology, or urinalysis parameters. No macroscopic or microscopic changes were attributable to intravitreal administration of TA. Food consumption and body weight were unaffected by drug administration. Conclusions: Three cycles of triamcinolone administered by intravitreal injection at a dose of 2 mg were well tolerated and did not result in any toxic effects on the ocular structures in general and to the retina in particular.
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