An exploratory microdialysis study to assess the ocular pharmacokinetics of ciprofloxacin eye drops in rabbits

Purpose: Despite the high frequency of use, data regarding the ocular in vivo pharmacokinetics (PK) of topically applied antibiotics are sparse. This study seeks to investigate the PK of the widely used fluoroquinolone ciprofloxacin by means of in vivo microdialysis. Methods: Twelve New Zealand white rabbits were included in the experiments. Under general anesthesia, microdialysis probes were implanted in the anterior chamber and the posterior segment of the same eye. After a period of 90 min after implantation, one drop of ciprofloxacin was administered onto the ocular surface. Microdialysis samples of the anterior chamber and the vitreous were collected every 30 min for 6 h. Relative recovery was assessed by retrodialysis to calculate absolute concentration values. Samples were analyzed using HPLC. Results: In the anterior chamber, the maximum total drug concentration (C_max) amounted to 0.373 ± 0.281 mg/ mL and was reached (T_max) after 116 ± 36 min. Calculated area under the concentration-time curve AUC(0-n) for ciprofloxacin in the anterior chamber was 78.8 ± 47.1 μg min/mL. For the vitreous, C_max was 0.02 ± 0.03 mg/ mL and maximum drug concentration was reached 107 ± 60 min after topical administration. AUC(0-n) for ciprofloxacin in the vitreous was 0.269 ± 0.370 μg min/mL. Conclusion: Microdialysis is a suitable method to assess in vivo pharmacokinetic profiles in the anterior chamber and in the vitreous. In the anterior chamber, maximum drug concentration was reached ∗2 h after single drug administration. Although the drug concentration in the vitreous was considerably lower, time course of drug concentration was comparable.