Human pharmacokinetics and distribution in various tissues of ceftriaxone

Multiple-dose pharmacokinetics of ceftriaxone were investigated in 7 patients with bronchopneumonia using an intramuscular regimen of 1 g given every 24 h for 7 days. Serum, sputum, and urine samples were collected serially following the first dose (day 1) and last dose (day 7). Mean peak serum concentrations of ceftriaxone occurred at 2 h on both days and were 67.8 and 75.1 micrograms/ml, respectively, on day 1 and day 7. Ceftriaxone had a half-life of 6.9 h on day 1 and 7.4 h on day 7. The half-life of ceftriaxone in sputum was 5.9 and 6.6 h, respectively, on days 1 and 7. Approximately 50% of the dose of ceftriaxone was recovered in the urine within 24 h on day 1, 60% on day 7. Tissue distribution of ceftriaxone was determined in 103 patients following intramuscular administration of a single 1-gram dose at different times up to 24 h prior to surgery. High concentrations of ceftriaxone were found in lung, tonsil, middle ear mucosa, and nasal mucosa, and therapeutic levels of ceftriaxone persisted for 24 h after administration.