Vitreous and aqueous penetration of orally and topically administered moxifloxacin.

Aim: It was the aim of this study to compare the pharmacokinetics of moxifloxacin (MFLX) hydrochloride in rabbits after topical and oral administration.

Methods: Three 50-μl applications of MFLX (0.5%) topical ophthalmic solution were instilled into the cul-de-sac of New Zealand white rabbits at 15-min intervals. Aqueous and vitreous samples were collected and analyzed 30-240 min after the final instillation. Assays were performed using high-performance liquid chromatography. MFLX (16 mg/kg of body weight) was administered orally. Drug concentrations in aqueous, vitreous and serum samples, collected at 30-360 min after administration, were determined using high-performance liquid chromatography.

Results: After topical administration, the maximum concentrations of MFLX in the aqueous and vitreous samples were 10.2 ± 1.6 μg/ml (30 min; n = 6) and 0.10 ± 0.03 μg/ml (30 min; n = 6), respectively. After oral administration, the maximum concentrations in the aqueous, vitreous and serum samples were 0.9 ± 0.3 μg/ml (120 min; n = 6), 0.7 ± 0.2 μg/ml (240 min; n = 6) and 1.6 ± 0.9 μg/ml (120 min; n = 6), respectively. The percentages of serum MFLX concentration in the aqueous and vitreous samples after oral administration were 55.2 and 41.7%, respectively.

Conclusions: The aqueous concentration of MFLX was about 10-fold higher after topical than after oral administration. However, intravitreal MFLX concentrations after oral administration were about 7-fold higher than those after topical administration. The MFLX concentrations in the aqueous humor following oral administration exceeded the minimum inhibitory concentration for 90% of the bacteria involved in ocular infection.