Placental transfer of furosemide.

After oral administration of furosemide to 18 pregnant women on the day of delivery, substantial concentrations of the drug were detected in umbilical cord vein plasma as well as in amniotic fluid. The ratio between the furosemide concentrations in maternal vein plasma and in umbilical cord plasma increased with time and approximated unity at 8 to 10 hr after administration of the drug. The plasma half-life of furosemide appeared to be longer in the mothers than in nonpregnant healthy volunteers. In one patient the plasma level of furosemide was constant during 5 hr of observation.