Passage of drugs through different intraocular microdialysis membranes

Abstract

• Background: Since drug penetration from the blood to the vitreous body is very poor, it is important to find means other than systemic delivery to reach necessary intraocular concentrations of drugs. This study represents a step in this direction. • Method: Microdialysis probes implanted intraocularly in rabbits were perfused with different substances, mainly drugs. The substances belonged to three groups, antibiotics, corticosteroids and cytostatics, and were: benzylpenicillin and cefuroxim; triamcinolone and dexamethasone; daunomycin and 5-fluorouracil. In addition, three substances of different molecular weights were tested: formic acid (MW 70), glucose (MW 189) and inulin (MW ca. 5200). • Results: 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 into the vitreous at a rate of about 10–20% of the perfusate concentration. Membranes with different dimensions and the above-mentioned two materials have also been screened for their transport properties in vitro. No differences were found between the two membrane materials, polycarbonate and polyamide. The net dialysis is strongly dependent on the probe geometry. • Conclusions: We have shown that the above-mentioned substances penetrate into the vitreous body of rabbits through an implanted microdialysis membrane. This is of importance for the development of new means of intraocular drug administration.