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MR Robinson, H Kim, N Collins, M Fronheiser, S Lee, J Sullivan, P Yuan, G Byrnes, J Baffi, K Csaky; One-Piece Silicone Intravitreal Implants for Sustained Drug Release . Invest. Ophthalmol. Vis. Sci. 2002;43(13):2297.
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Purpose: Current manufacturing methods for non-biodegradable intraocular devices: 1) can produce variable amounts of polymer surrounding a central drug pellet during the coating process producing variable release rates 2) frequently involve fusion of the pellet/polymer complex to a suture platform made of a different polymer that can dissociate in the eye, 3) are expensive to produce. We describe the use of Teflon moulds to produce one-piece silicone implants for sustained delivery of drug into the vitreous. Methods: Teflon moulds were fabricated with the dimensions of 25.4 mm diameter and 9.6 mm in height. This size enables the mould to fit into a 50 ml polypropylene centrifuge tube for periodic degassing during the implant assembly. A cavity of 4.25 mm, 1.4 mm in depth was made at one end of the mould using a milling machine. A 23 guage needle projected from the suture platform end where a polyester mesh, 2 x 2 mm, is placed in the silicone to reinforce the silicone. Implants of two designs were made in the moulds: Design A a matrix of 20% by weight of 2-methoxystradiol (2ME2) mixed with silicone (MED2-4213, Nusil Tech.) 2) Design B a reservoir using a 3 mm compressed pellet of 2ME2 (3.5 mg weight) with silicone (MED1-4213). The in vitro release rates were determined by measuring drug release from the implants over time by HPLC. Results: Both implants produced an initial burst of drug over the first week followed by steady state release of 9.6 ± 0.05 and 3.7 ± 0.3 ug/day (measured at 7 weeks) for designs A and B, respectively. Conclusions: Teflon moulds can efficiently produce one-piece intravitreal implants with high reproducibility and consistent release rates. The implant using a silicone/drug composite (design A) can significantly increase drug release rates over a more conventional design (design B).
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