Intrapulmonary pharmacokinetics of clarithromycin and of erythromycin

The intrapulmonary pharmacokinetics of orally administered clarithromycin (500 mg every 12 h for five doses) or erythromycin (250 mg every 6 h for nine doses) were studied in 32 healthy adult volunteers. Four of the subjects, two in the clarithromycin group and two in the erythromycin group, were smokers. Bronchoscopy, bronchoalveolar lavage, and venipuncture were performed at 4, 8, 12, 24, and 48 h after administration of the last dose of clarithromycin and at 4, 8, and 12 h after administration of the last dose of erythromycin. Clarithromycin was measured by high-performance liquid chromatography, and erythromycin was measured by a microbiological assay. No systemic sedation was used. There were no major adverse events. The concentrations of antibiotics in epithelial lining fluid (ELF) were calculated by the urea dilution method. The volumes (mean +/- standard deviation) of ELF were 1.9 +/- 2.0 ml and 1.5 +/- 0.7 ml in the clarithromycin and erythromycin groups, respectively (P > 0.05). There was no effect of smoking on the amount of bronchoalveolar lavage fluid recovered, the volume of ELF, or the number of erythrocytes present in the lavage fluid (P > 0.05 for all comparisons). The total number of alveolar cells, however, was almost threefold greater in the smokers versus that in the nonsmokers (P < 0.05). Clarithromycin was concentrated in ELF (range, 72.1 +/- 73.0 micrograms/ml at 8 h to 11.9 +/- 3.6 micrograms/ml at 24 h) and alveolar cells (range, 505.8 +/- 293.1 micrograms/ml at 4 h to 17.0 +/- 34.0 micrograms/ml at 48 h). 14-(R)-Hydroxyclarithromycin was also present in these compartments, but at lower concentrations than the parent compound. The concentrations of erythromycin in ELF and alveolar cells were low at 4, 8, and 12 h following the last dose of drug (range, 0 to 0.8 +/- microgram/ml in ELF and 0 to 0.8 +/- 1.3 microgram/ml in alveolar cells). The clinical significance of any antibiotic concentrations in these compartments in unclear. The data suggest, and we conclude, that clarithromycin may be a useful drug in the treatment of pulmonary infections, particularly those caused by intracellular organisms.