Five milligram of cytarabine was injected subconjunctivally in the rabbit eye, and its concentration changes in the cornea, aqueous humor, and conjuncitva and sclera (both at the injection site and 180°away from it)were determined by radioassay. The cytarabine concentrations in the conjunctiva and the sclera at the injection were 1217, 612㎍/g at one hour. The cytarabine concentrations in the conjunctiva and the sclera at 180°away from the injection site were 36.1, 31.6㎍/g at one hour. At five hour, the cytarabine concentrations in the conjunctiva and the sclera at the injection site were similar to those 180°away from it, both averaging about 6.2㎍/g. They decreased to 0.9 through 1.9㎍/g, while the latter was 0.09㎎/L at one hour, the former decreased to 0.9㎍g, while the latter was 00.9㎎/L at 24 hours. The cytarabine concentrations in the conjunctiva and the sclera at 24 hours were still above the reported 50% inhibition levels(ID50) for the cultured conjunctival fibroblast.
These findings have potential clinical implications for the safe use of cytarabine