Intravitreal concentrations of some drugs administered with microdialysis

Intraocular microdialysis was used to administer the drugs 5-fluorouracil, benzyl penicillin, daunomycin and dexamethasone into the vitreal space of rabbits. The purpose of the study was to investigate if therapeutic concentrations could be obtained with this administration method. After administering the drugs in labelled form, the attained concentrations were assessed by counting the radioactivity in the entire vitreous. For benzyl penicillin, the concentration was 2 microM, for dexamethasone it was 1.2 x 10(-7) M, and for daunomycin it was 1.2 microM, which are considered to be within the therapeutic ranges. For 5-fluorouracil, the corresponding concentration was 5 x 10(-5) M which probably is below the therapeutic level, when comparing with single-dose injections.