Pharmacokinetics of enoxacin and its penetration into bronchial secretions and lung tissue

Pharmacokinetic data were obtained from four healthy volunteers after oral administration of a single 400 or 600 mg dose of enoxacin. Enoxacin was absorbed quickly and absorption was increased when enoxacin was ingested after a meal. Renal clearance of enoxacin and 4-oxo-enoxacin decreased after simultaneous administration of probenecid. In addition, pharmacokinetic parameters of enoxacin and its 4-oxo metabolite were determined for plasma and sputum from 19 patients treated with enoxacin, 400 or 600 mg bd, for a respiratory tract infection. The half-life of both enoxacin and 4-oxo-enoxacin was 5–6 h; during treatment with 400 and 600 mg bd, the plasma concentrations exceeded MIC values for most bacteria isolated in respiratory tract infections, including most Pseudomonas aeruginosa strains; Streptococcus pneumoniae was an exception. Diffusion from plasma to sputum was approximately 100%. Of an ingested dose, 60–65% was recovered in the urine in 24 h. In a third study, a single 600 mg dose of enoxacin was given to 15 patients undergoing thoracotomy. Subsequent lung tissue concentrations of enoxacin were significantly higher than plasma concentrations at the same time after ingestion.