Tobramycin: maternal-fetal pharmacology

Area of Science:

• Pharmacology
• Obstetrics
• Neonatology

Background:

• Maternal infections during pregnancy necessitate antimicrobial therapy, raising concerns about fetal drug exposure.
• Understanding maternal-fetal drug transfer is crucial for optimizing treatment and minimizing potential fetal risks.

Purpose of the Study:

• To investigate the maternal-fetal transfer and fetal distribution of tobramycin (TBM).
• To assess the impact of gestational age and fetal maturation on TBM pharmacokinetics.

Main Methods:

• A single intramuscular dose of tobramycin was administered to pregnant patients prior to hysterectomy.
• Tobramycin concentrations were measured in maternal serum, fetal tissues, and fluids using microbiological assays.

Main Results:

• Maternal TBM pharmacokinetics were similar to nonpregnant adults.
• Fetal serum TBM levels were low, with a longer half-life (5.2 h).
• TBM concentrations varied in fetal tissues and fluids, with higher levels in placental tissue, second-trimester amniotic fluid, and fetal kidney, correlating with maturation.

Conclusions:

• Tobramycin transfer to the fetus occurs, with distribution influenced by gestational age and organ development.
• Fetal kidney and second-trimester amniotic fluid accumulate higher TBM concentrations.
• Fetal pharmacokinetic data are essential for evaluating the risk-benefit profile of tobramycin use in pregnant patients.