PASSAGE OF DRUGS THROUGH DIFFERENT INTRAOCULAR MICRODIALYSIS MEMBRANES

Background: Since drug penetration from the blood to the vitreous body is very poor, it is important to find means other than systemic deliv ery to reach necessary intraocular concentrations of drugs. This study represents a step in this direction. Method: Microdialysis probes imp lanted intraocularly in rabbits were perfused with different substance s, mainly drugs. The substances belonged to three groups, antibiotics, corticosteroids and cytostatics, and were: benzylpenicillin and cefur oxim; triamcinolone and dexamethasone; daunomycin and 5-fluorouracil. In addition, three substances of different molecular weights were test ed: formic acid (MW 70), glucose (MW 189) and inulin (MW ca. 5200). Re sults: When used in tracer concentrations, some lipophilic drugs stick to polycarbonate but not to polyamide membranes. The latter material has therefore been used in all intraocular perfusions. All substances except inulin were found to diffuse through the polyamide membrane int o the vitreous at a rate of about 10-20% of the perfusate concentratio n. Membranes with different dimensions and the above-mentioned two mat erials have also been screened for their transport properties in vitro . No differences were found between the two membrane materials, polyca rbonate and polyamide. The net dialysis is strongly dependent on the p robe geometry. Conclusions: We have shown that the above-mentioned sub stances penetrate into the vitreous body of rabbits through an implant ed microdialysis membrane. This is of importance for the development o f new means of intraocular drug administration.