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J.A. Cardillo, F. Paganelli, R.A. Costa, A.A. Silva, A.G. OLiveira, A.A. S. Lima–Filho, M.E. Farah, R. Belfort, Jr., B.D. Kuppermann; Intravitreal Bioerudivel Sustained–Release Triamcinolone Microspheres System (RETAAC): Safety and Pharmacokinetic in the Rabbit Eye and a Preliminary Report of its Potential Usefulness for the Treatment Diabetic Macular Edema . Invest. Ophthalmol. Vis. Sci. 2006;47(13):3886.
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To study the potential of RETAAC in the rabbit eye and to report the initial findings in patients with diabetic macular edema.
The triamcinolone (TA) loading efficiency and quantitative analysis were determined by HPLC. In vitro, 1mg of TA or RETAAC was incubated in phosphate buffer and the concentrations of TA released determined against the time. In vivo, 1mg/0.1mL of TA or RETAAC was injected into the vitreous of sixty rabbits utilizing a 27–gauge syringe and the TA concentration determined in the aqueous and vitreous humors up to 120 days. To assess toxicity serial electron microcopy and electrophysiology examinations were performed. A pilot case series of ten patients with diabetic macular edema treated with RETAAC was carried out. Changes in visual acuity (VA) and central macular thickness (CMT) were measured during a six–month follow–up. Potential treatment complications were monitored.
The RETAAC showed a uniform particle size (1µm +.0.1). In vitro, the time release was 3 hs for TA and 144 hs for RETAAC. In vivo, the free TA did not remain above the active for more than 24 days in both, aqueous and vitreous humors. For RETAAC, the theoretical intravitreal therapeutic level of 25µg/ml remained for up to 120 days. No toxicity was observed. Clinically, preliminary results suggest a trend towards improved VA and reduced CMT up to six months. Safety analysis has raised no issues.
RETAAC demonstrated a more sustained in vitro and in vivo release profile than its free form. Taken together with its minimally invasive delivery requirements, this new system may characterize an optimized approach, overcoming most of the implantation barriers faced with the conventional pellet system. Clinical findings neither advocate nor support the use of RETAAC for diabetic macular edema, but imply that this system may be well tolerated and represents a promising approach for the intraocular delivery of drugs.
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