Penetration of enoxacin into human bronchial mucosa

Enoxacin is a new quinolone-azaquinolone antibiotic that possesses in vitro activity against a broad spectrum of bacteria including Pseudomonas aeruginosa. We studied the distribution ratio of enoxacin between plasma and bronchial mucosa under steady-state conditions. Bronchial mucosal biopsies were obtained during fiberoptic bronchoscopy in 18 patients after receiving enoxacin, 400 mg every 12 h for 4 days. Bronchial mucosa and plasma were sampled at 3, 4, or 5 h (6 patients each) after the fifth day morning 400-mg dose and assayed for enoxacin by high pressure liquid chromatography. There was no significant difference in the enoxacin bronchial mucosa to plasma concentration ratios at the 3 sampling times. This suggests that equilibrium between bronchial mucosa and plasma had been achieved within 3 h after dose. The mean (SD) bronchial mucosal concentration for all patients was 117.0 (47.8) micrograms/g, the mean (SD) plasma concentration was 3.1 (1.1) micrograms/ml, and the mean (SD) ratio was 46.8 (45.9). The bronchial mucosal enoxacin concentrations were significantly higher than the minimal inhibitory concentrations for common respiratory pathogens including Ps. aeruginosa (90% inhibited by 2.0 micrograms/ml). These results provide pharmacokinetic support for the use of enoxacin in gram-negative bronchial infections.