Posterior juxtascleral injection of anecortave acetate: magnetic resonance and echographic imaging and localization in rabbit eyes.

Abstract

To confirm juxtascleral delivery of anecortave acetate in rabbit eyes by ocular imaging techniques and to determine drug localization and distribution as a function of time after injection. Four female New Zealand white rabbits (weight, 2.5-3.0 kg) received a single juxtascleral posterior sub-Tenon capsule injection of 0.5 mL or 1 mL of 30 mg/mL anecortave acetate. Rabbit eyes were imaged with ultrasonography and magnetic resonance imaging (MRI) before injection, immediately after injection, and at 2 hours, 1 week, and 4 weeks after injection. Rabbit eyes were also imaged with b-mode ultrasonography during the juxtascleral injections. Ultrasonography and MRI demonstrated that juxtascleral posterior sub-Tenon capsule injection of anecortave acetate effectively delivered the drug in direct apposition to the posterior pole of the rabbit eye. The drug remained in the juxtascleral site for at least 5 weeks. The drug was visualized clearly by MRI immediately after injection, decreasing in intensity thereafter. Cannula insertion and the drug delivery process were clearly visualized by real-time ultrasound analysis. Immediately after drug injection, ultrasonography indirectly localized anecortave acetate localization as an echolucent zone posterior to the scleral surface. At the later time points, however, the juxtascleral location of the drug was verified with ultrasonography as a relatively echogenic focus in the same location. Juxtascleral administration of anecortave acetate via a posterior sub-Tenon capsule approach effectively delivered the drug to the desired position in direct apposition to the globe posteriorly. MRI and ultrasonography both demonstrated that anecortave acetate remained localized to this location for at least 5 weeks after initial injection.