The distribution of gentamicin in the rabbit cornea following iontophoresis to the central cornea

The purpose of this study was to evaluate the penetration of gentamicin int o the central, midperipheral and peripheral cornea of rabbits following ion tophoresis to the central 3 mm of the cornea. Four groups (groups 1-4) of five rabbits tone eye per rabbit) underwent cor neal iontophoresis using gentamicin dissolved in agar. Low (1 mg/ml) and hi gh (10 mg/ml) concentrations of gentamicin in agar were used for one or ten minutes. Two control groups (groups 5 and 6) of five eyes each underwent m ock iontophoresis with low and high concentrations of agar-gentamicin mixtu re. Following sacrifice of the rabbits, the central, midperipheral and peri pheral parts of each cornea were excised. Gentamicin concentration was dete rmined in each part of every cornea. High concentrations of gentamicin (951.6 +/- 369.4 mu g/ml to 26.6 +/- 41.3 4 mu g/ml) were obtained in the central parts of all the iontophoresis-trea ted corneas. In each group, except group 6, central corneas had higher conc entrations of gentamicin compared to midperipheral corneas (p = 0.038 to p = 0.021), and midperipheral corneas had higher levels than peripheral corne as (p = 0.038 to p = 0.021). Following iontophoresis, gentamicin is found in all portions of the corneas ; however, the highest concentration of the drug remains in the central cor nea.