Evaluation of vitreous levels of gatifloxacin after systemic administration in inflamed and non‐inflamed eyes

. Purpose:  This study aimed to evaluate the human vitreous penetration of gatifloxacin in inflamed and non-inflamed eyes after oral administration. Methods:  Vitreous penetration of single-dose (400 mg) oral gatifloxacin was evaluated in patients (n = 33) undergoing vitreous tap during the standard procedure for intravitreal antibiotic injection for acute postoperative endophthalmitis at various time-points. Vitreous penetration of 400 mg oral gatifloxacin was evaluated in the non-inflamed eyes of patients (n = 33) undergoing pars plana vitrectomy at similar time-points. The study was extended to evaluate the vitreous penetration of single-dose oral (800 mg) gatifloxacin at a single time-point in inflamed (n = 10) and non-inflamed (n = 11) eyes. Results:  After 400 mg oral gatifloxacin, inflamed eyes showed mean vitreous concentrations of 0.58±0.19μg/ml, 1.33±0.33 μg/ml and 1.30 ± 0.23 μg/ml at 2, 4 and 6 hours, respectively. The levels reached at 2 and 4 hours were found to be significantly increased compared with those in non-inflamed eyes. At the 800-mg dose, 4-hour vitreous levels in inflamed and non-inflamed eyes were 1.57 ± 0.3 μg/ml and 1.42 ± 0.24 μg/ml, respectively. Although the increased dose of gatifloxacin elevated plasma concentration, it failed to raise vitreous levels significantly higher than the 400-mg dose at the 4-hour time-point. Conclusions:  Orally administered gatifloxacin achieves therapeutic levels in both inflamed and non-inflamed human eyes with a spectrum covering the bacterial species most frequently involved in the various causes of endophthalmitis. However, the levels achieved were below the MIC90 for Pseudomonas aureginosa and Enterococcus.