[Application of microdialysis for pharmacokinetic study in rabbit anterior chamber]

We evaluated a microdialysis technique for analyzing the pharmacokinetics of instilled or orally administered ofloxacin in the anterior chamber of pigmented rabbits. A microdialysis probe was inserted into the anterior chamber and was perfused (2 microliters/min) with Ringer solution using a microinjection pump. Two hours later, 20 microliters of 0.15 and 0.3% ofloxacin was instilled into an eye, or 20 mg/kg of the drug was administered into the stomach through an intubated catheter. Dialysate was then collected every 15 or 20 min for 6 (instillation) or 8 (oral administration) hours. Ofloxacin concentration in dialysates was determined with a HPLC-spectrofluorometry system. Ofloxacin levels in dialysates increased after the instillation in a dose-related manner, reached a maximum at 30 and 45 min, and then decreased gradually with t1/2 of 136 and 114 min after the 0.15% and 0.3% instillation, respectively. After oral administration, ofloxacin levels in dialysates reached a maximum at 120 min and decreased with t1/2 of 175 min. These data suggest the usefulness of microdialysis for pharmacokinetic studies in the anterior chamber, since continuous and stable data can be obtained from each animal.