Pharmacokinetics and sputum penetration of enoxacin after twice daily oral dosing for seven days.

The ability of enoxacin to penetrate into sputum and its distribution and elimination characteristics after dosing to steady state were determined in six subjects with permanent tracheostomies. At steady state the mean trough level of enoxacin in sputum was 1.75 +/- 0.70 mg/kg (mean +/- S.D.), and the corresponding level in plasma was 1.23 +/- 0.32 mg/l. The mean peak sputum concentration at steady state was 7.12 +/- 4.21 mg/kg with the corresponding level in plasma being 4.54 +/- 1.34 mg/l. The ratio of the mean trough concentration of enoxacin in sputum to that in plasma was 1.42 +/- 0.36, and the ratio of the mean peak concentrations was 1.67 +/- 1.07. The pharmacokinetics of enoxacin in sputum were similar to those in plasma, the only significant difference being between the mean times to reach peak concentration (T-max) which were 2.62 +/- 1.04 and 0.92 +/- 0.44 h in sputum and plasma respectively (P less than 0.01). After reaching steady state, the mean area under the plasma time-concentration curve (AUC) from 0 to 12 h (the dosing interval) was 26.6 +/- 5.9 mg/h/l, and the mean AUC (0-12) for sputum was 40.9 +/- 21.8 mg/h/kg. The mean apparent total clearance was 259.6 +/- 48.8 ml/min and the mean apparent volume of distribution was 169.6 +/- 30.51. Enoxacin exhibits a high degree of penetration into sputum which may prove useful in the treatment of bacterial infections of the respiratory tract.