BRONCHIAL SECRETION LEVELS OF AMIKACIN

Amikacin was given to 14 noninfected men as three consecutive intramuscular injections (7.5 mg/kg) at 12-h intervals. Serum and bronchial secretion specimens were obtained at various times during flexible fiberoptic bronchoscopy after the final dose. Serum and bronchial secretion concentrations obtained between 1.5 and 2.0 h after the final dose ranged from 17 to 40 μg/ml and 2.3 to 8.4 μg/ml with a mean of 23.7 ± 2.9 and 5.23 ± 1.5 μg/ml, ±1 standard error of the mean, related with the highest serum concentration (r = 0.83, P < 0.001), and all concurrent serum and bronchial secretion concentrations demonstrated a significant correlation (r = 0.82, P < 0.001). Clearance occurred at the same rate (half-life serum = 2.84 h; half-life of bronchial secretion = 2.60 h, P > 0.5). The mean bronchial secretion concentration of 15 specimens obtained more than 7 h after the final dose was less than 1.0 μg/ml, with a range from 0.3 to 1.6μg/ml. It is concluded that amikacin may achieve minimal inhibitory concentrations for 1 to 2 h after the final dose. However, levels fall below the reported minimal inhibitory concentrations against negative bacteria 6 to 7 h after the final dose. Furthermore, bronchial secretion levels may never reach the minimal inhibitory concentration against Pseudomonas aeruginosa.