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.