The effect of long-term use and inflammation on the ocular penetration of topical ofloxacin.

PURPOSE

To study the penetration of ofloxacin into the aqueous and vitreous humors after long-term topical administration and to investigate the effects of inflammation on drug penetration in rabbits.

METHODS

A standardized model of intraocular infection after penetrating injury was achieved in the right eyes of 16 rabbits. The animals were randomly and equally divided into two groups. The intact left eyes of the groups were maintained as the control. Ofloxacin eyedrops (0.3%) were instilled into all eyes at a frequency of 2 drops every hour for 7 hours in the first group and for 14 hours in the second group. Half an hour after the last drop, samples of the aqueous and vitreous humors were taken and ofloxacin concentrations were measured by using HPLC.

RESULTS

The mean aqueous humor concentrations of ofloxacin in control eyes after 7 and 14 hours of instillation were: 1.45 +/- 0.93 microg/ml and 2.48 +/- 0.33 microg/ml, respectively; those in infected eyes 2.35 +/- 1. 84 microg/ml and 3.49 +/- 1.47 microg/ml, respectively. However the differences among the groups were not significant (p > 0.05). The vitreous ofloxacin concentrations in the control eyes were similar after 7 and 14 hours of instillation (0.23 +/- 0.14 microg/ml, 0.27 +/- 0.10 microg/ml, respectively). In infected eyes, the mean vitreous ofloxacin concentration after 14 hour of instillation was significantly higher than that in control eyes (p < 0.05; 0.4 +/- 0. 09 microg/ml, 0.29 +/- 0.11 microg/ml, respectively). The mean vitreous ofloxacin concentration in infected eyes after 14 hours instillation was not significantly higher than that after 7 hours instillation.

CONCLUSIONS

Topical ofloxacin instillation for 7 or 14 hours yields aqueous concentrations above the MIC(90) for common ocular pathogens. Prolonged application and the presence of inflammation increased the penetration of ofloxacin into the vitreous humor.