Evaluation of the amoxicillin concentrations in amniotic fluid, placenta, umbilical cord blood and maternal serum two hours after intravenous administration.

OBJECTIVES: The aims of this study were to evaluate amoxicillin concentrations in amniotic fluid, placenta, umbilical cord blood and maternal blood two hours after intravenous administration to assess obstetric and non-obstetric factors that could have influences on the penetration of the antibiotic into the examined tissues and to analyze the sensitivity to amoxicillin of the most common pathogens isolated from the genital tract.

METHODS: A total of 35 full-term pregnant women who qualified for elective Caesarean delivery were included in the study. Amoxicillin at a dose of 1000 mg was administered prior to surgery. Amoxicillin levels were determined by diffusion microbial assay.

RESULTS: The drug concentration was highest in umbilical cord blood compared with amniotic fluid, maternal blood and placenta (4.20±1.06 µg/g versus 3.96±0.79 µg/g, 3.22±0.64 µg/g and 2.81±0.64 µg/g, respectively). Obstetric and non-obstetric factors had no influence on the amoxicillin concentration. The most common bacteria isolated from the genital tracts of pregnant women (Streptococcus agalactiae, Enterococcus faecalis, Escherichia coli) were sensitive to amoxicillin. The MIC for the sensitive strain of Streptococcus agalactiae was seen in the majority of tissues of all of the patients; however, the MICs for E. faecalis and E. coli were not observed in any compartment.

CONCLUSIONS: Amoxicillin proved to have good penetration into the fetal tissues and placenta after intravenous administration. The most common bacteria isolated from the genital tracts of pregnant women were sensitive to amoxicillin. Pregnancy complications were not found to have an influence on the amoxicillin concentrations in the examined tissues.