Ceftriaxone distribution between maternal blood and fetal blood and tissues at parturition and between blood and milk postpartum.

The penetration of ceftriaxone into the fetus at parturition was studied in 17 subjects. Despite its high protein binding, ceftriaxone quickly reached the umbilical cord blood, amniotic fluid, and placenta, achieving substantial concentrations, which then disappeared, with elimination half-lives of approximately 6 h, identical to that of the mother. The elimination half-life of ceftriaxone of 5 to 6 h in these mothers was somewhat shorter than that reported for normal subjects. The concentrations of ceftriaxone achieved in fetal tissues were sufficient for therapeutic effects. The penetration of ceftriaxone into milk was studied 3 days postpartum in 20 other patients. This antimicrobial agent entered breast milk rapidly and disappeared with a half-life of 12 to 17 h. The concentrations achieved were only 3 to 4% of those in maternal serum and were most likely of little clinical relevance.