Transabdominal amnioinfusion of gentamicin: a pharmakokinetic study of maternal plasma and intraamniotic levels

OBJECTIVE: To study the pharmacokinetics of gentamicin alter iransabdominal amnioinfusion compared with parenteral administration. STUDY DESIGN: 33 women admitted for mid-trimester termination of pregnancy bv iransabdominal intraainniotic prostaglandin F2α were assigned randomly to 2 groups. Sixteen women were given 10 nig intraainniotic ainnioinfhsion of gentamicin and 17 received a single dose of 80 nig gentamicin intravenouslv. Samples of maternal blood and amniotic fluid were obtained and fetal blood samples were drawn after abortus was expulsed. The study protocol was approved bv the Human Investigations Committee. RESULTS: Following gentamiein administration into the amniotic cavity, maternal plasma concentrations were herv low (median of 0.28 μg/ml). Amniotic fluid reached very high levels (median of 46 μg/ml) that were sustained for periods longer than 2-1 hours. Median fetal plasma levels were 0.4 μg/ml. Intravenous gentamicin yielded peak plasma levels of 5.7 jig/nil and below 1 μ/ml at 4 hours and subsequently. Amniotic fluid concentrations wert' low throughout (median of 0.35 μg/ml). CONCLUSIONS: Intraamniolic administration of gentamiein results in high, sustained levels in the amniotic cavity and low concentrations in maternal and fetal blood. On the other hand, imravenousK, the drug fails to reach a therapeutic level in the amniotic cavity. We suggest that iransabdominal imraamniotic gentamicin be used to obtain high local concentrations of the antibiotic without reaching toxic levels in the mother or feiuv.