Intraocular distribution of intravitreally administered amphotericin B in normal and vitrectomized eyes

A study was performed to determine how amphotericin B is distributed in the eye after direct intravitreal injection. Radiolabeled amphotericin B was administered by direct injection into the vitreous space of unmodified phakic control or vitrectomized aphakic eyes in the rabbit model. The eyes were removed at different post-injection times, frozen and dissected into anatomical subparts of cornea, aqueous, iris, lens, vitreous and sclera-choroid-retina. The parts were assayed for total radioactivity (expressed as remaining amphotericin B). No accumulation of drug was observed in the cornea, lens, iris or aqueous region. The majority of drug was found in the vitreous cavity. The rate of disappearance of radiolabeled drug or radiolabeled drug degradation products from the vitreous space was similar to the rate of disappearance from the eye. However, progressive accumulation of radioactivity was observed in the sclera-choroid-retina tissue in the unmodified phakic eyes. This was not observed in vitrectomized aphakic eyes. The accumulated radioactivity could have represented drug degradation products or active drug. These results shed light on the distribution of amphotericin B in the eye after direct intravitreal injection, a procedure often employed clinically for fungal endophthalmitis.