Pharmacokinetics, electrophysiological, and morphological effects of the intravitreal injection of mycophenolic acid in rabbits.

Purpose: To determine the half-life of mycophenolic acid (MPA) in the vitreous of New Zealand albino rabbits after intravitreal injection and the retinal toxicity of different doses of MPA. Methods: Ten micrograms of MPA (Roche Bioscience, Palo Alto, CA) was injected in the vitreous of 16 rabbits, animals were sacrificed at different time-points, and vitreous samples underwent high-performance liquid chromatography. For functional and morphological studies, 5 doses of MPA (0.05, 0.5, 2, 10, and 100 mu g) were injected in the vitreous of 20 rabbits. As control, contralateral eyes were injected with aqueous vehicle. Electroretinograms (ERGs) were recorded before injection and at days 7, 15, and 30. Animals were sacrificed on day 30 and retinas were analyzed under light microscopy. Results: MPA half-life in the vitreous was 5.0 +/- 0.3 days. ERG revealed photoreceptor functional impairment in eyes injected with 0.5 mu g and higher on day 30, while eyes injected with 100 mu g presented the same changes already from day 15. No morphological change was found. Conclusions: MPA vitreous half-life is 5.0 days. Intravitreal injection of 0.5 mu g MPA and higher causes dose- and time-related photoreceptor sensitivity decrease in rabbits. The MPA dose of 0.05 mu g may be safe for intravitreal use in rabbits.