Pharmacokinetics and retinal toxicity of intravitreal liposome-encapsulated 5-fluorouridine

Background: Fluoropyrimidines may be effective in preventing proliferative vitreoretinopathy after repair of complicated retinal detachments. Liposome encapsulation of these antiproliferative drugs may extend the intravitreal half-life and increase their efficacy. Methods: The current study evaluated the pharma-cokinetic behavior of intravitreally injected 5-fluorouridine (5-FUR), free and encapsulated in liposomes, either conventionally or coated with collagen into 25 New Zealand rabbits. Additionally, we investigated the retinal toxicity of intravitreal injections of 100, 250 and 500 �g as well as 1 mg 5-FUR as free drug or encapsulated in liposomes in the rabbit eye. Results: The half-life of free 5-FUR after liposome injection into the vitreous cavity was 18.17+2.43 h, considerably longer than the half-life of free 5-FUR (0.82 h). Electrophysiologic tests did not show any changes in latency and a-wave amplitude and minimal changes in the b-wave amplitude. Histopathologic studies revealed integrity of the inner limiting membrane, and mild vacuolization in the outer retina. Conclusion: Encapsulation of 5-FUR within liposomes markedly increases its intravitreal half-life. Our study suggests that liposome-encapsulated 5-FUR is not toxic to the retina even at doses of 1 mg. © 1997 S. Karger AG, Basel.