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Z. Hoffelt, D. Hainsworth, B. Privett; Intravitreal vs. Subtenons Delivery of Avastin. Invest. Ophthalmol. Vis. Sci. 2008;49(13):1826.
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Bevacizumab (Avastin) has shown great promise in the treatment of choroidal neovascularization in macular degeneration. Currently, bevacizumab is delivered to the eye via an intravitreal injection. This type of injection poses many risks including endophthalmitis, hemorrhage and retinal detachment. We examined sub-tenon injection as an alternative delivery method for bevacizumab in a rabbit model to determine whether this less invasive delivery route would provide comparable intravitreal drug concentrations.
New Zealand White rabbits were used for this study.Group 1) 1.25mg of bevacizumab was injected intravitreally in 9 rabbits. Three rabbits were sacrificed at 1, 6, and 24 hours after injection.Group 2) 12.5mg of bevacizumab was injected in the sub-tenon space in 12 rabbits. Three rabbits were sacrificed at 6, 24, 48 and 96 hours after injection.Intravitreal concentration of bevacizumab was determined for all eyes by high-performance liquid chromatography.
Average vitreous bevacizumab concentrations (microgram/ml) following intravitreal injection were 79.5 at one hour; 113.1 at 6 hours; and 158.9 at 24 hours.Average vitreous bevacizumab concentrations (micrograms/ml) following sub-tenon injections were 3.1 at 6 hours; 1.9 at 24 hours; 5.0 at 48 hours and 11.8 at 96 hours.
Bevacizumab injected into the sub-tenon space results in measurable drug levels in the vitreous. These levels are less than the levels achieved through direct intravitreal injection. Whether these levels are adequate to inhibit neovascular membranes is unknown.
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