Azithromycin is an azalide
antibiotic. On the basis of data in adults,
azithromycin appears to have a greater distribution into tissues, a longer elimination half-life, and a lower incidence of adverse effects than the
macrolide antibiotic erythromycin. However, little about the pharmacokinetics of
azithromycin in children is known. The objective of our study was to characterize the pharmacokinetics of
azithromycin after
oral administration of multiple doses of
suspension to children with streptococcal
pharyngitis. Fourteen children (6 to 15 years of age) received a single oral dose of 10 mg of
azithromycin per kg of
body weight on day 1 followed by single daily doses of 5 mg/kg on days 2 to 5. Each child fasted overnight before receiving the final dose on day 5. Blood samples were collected at 0, 0.5, 1, 2, 4, 6, 8, 12, 24, 48, and 72 h after this last dose. Concentrations of
azithromycin in serum were measured by a specific high-performance liquid chromatography-mass spectrometry method. The mean +/- standard deviation for maximum concentration of
drug in serum, time to maximum concentration of
drug in serum, and area under the curve (0 to 24 h) were 383 +/- 142 ng/ml, 2.4 +/- 1.1 h, and 3,109 +/- 1,033 ng.h/ml, respectively. Concentrations in serum at 0 h (predose) and at 24, 48, and 72 h after the final dose were 67 +/- 31, 64 +/- 24, 41 +/- 17, and 29 +/- 14 ng/ml, respectively. Thus, once-daily administration of
azithromycin resulted in sustained systemic exposure to the
drug.