Liposomal entrapment of floxuridine.

Floxuridine was found to have an apparent initial entrapment within negatively charged sphingomyelin liposomes about three times higher than its parent, fluorouracil. The drug also diffused out of the liposomes at a much lower rate than fluorouracil. Substitution of lecithin for sphingomyelin destroyed the effect. Liposomal entrapment may provide enhanced stability and decreased toxicity of floxuridine, permitting wider therapeutic utilization of pyrimidine nucleosides.