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R. C. Siqueira, A. S. Cunha, Sr., S. L. Fialho, R. Jorge, Retina Research Team-Brazil; Pharmacokinetic and Toxicity Investigations of a 25 Gauge Implant With Dexamethasone Drug Delivery System (25 Gauge-DDS): A Pilot Study. Invest. Ophthalmol. Vis. Sci. 2007;48(13):255.
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To investigate the short-term safety and pharmacokinetic behavior of a intravitreal implants prepared with the biodegradable copolymer poly (lactide-co-glycolide) and containing dexamethasone, which was inserted through a 25 gauge trocar for transcleral cannula (25 gauge drug delivery system) in rabbit eyes.
A intravitreal implants prepared with the biodegradable copolymer poly (lactide-co-glycolide) and containing dexamethasone, was implanted into the posterior chamber of the right eyes of 18 new Zealand white rabbits using trocar for transcleral cannula (Accurus® 25-Gauge System, Alcon, Inc., USA). The implant containing dexamethasone (Group 1) was then inserted into the vitreous cavity of 12 rabbits and in 6 animals received the implant without drug using the same technique described above (control group).Serial slitlamp and indirect ophthalmoscopic examinations (including grading of intraocular inflammation) were performed. After 7, 14 and 21 days, the rabbits were euthanized and the globes were removed for histological examination and for determination of dexamethasone levels in the aqueous humor and in the vitreous. Analysis of dexamethasone concentrations was performed by ELISA.
Therapeutic level (150-4000 ng/ml) of dexamethasone was achieved throughout the experiment. These data show a drug-release profile that is derived from diffusional release during polymer erosion and disintegration of the polymeric matrix. The histological examination of the experimental eyes showed no structural changes in the operated eyes after 21 days of the insertion of the implant. The retinas exhibited normal morphological features and did not demonstrate any signs of toxicity or inflammatory cell infiltration
The biodegradable dexamethasone implant (25 gauge drug delivery system) developed in this pilot study was not toxic to the normal rabbit retina and provided a prolonged release of the drug within therapeutic levels in the vitreous cavity for at least 21 days after insertion. Controlled animal studies are currently being performed to test the long term safety of the implant in normal and diseased eyes.
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