Nifedipine concentrations in maternal and umbilical serum, amniotic fluid, breast milk and urine of mothers and offspring.

Eleven hypertensive pregnant patients were treated with nifedipine orally 10 mg thrice daily. At steady state, nifedipine concentration, measured by the high-performance liquid chromatographic method, was 4.3 +/- 1.0 ng/ml (mean +/- s.e.m.) in maternal serum in the third trimester of pregnancy. During delivery, the parent drug levels in maternal and umbilical serum and in amniotic fluid were 12.4 +/- 4.0, 8.6 +/- 2.3 and 2.5 +/- 1.2 ng/ml, respectively. Small amounts of nifedipine were found also in urine of the neonates. In breast milk, the nifedipine concentration was 4.1 +/- 0.8 ng/ml on the third day after delivery. The antihypertensive effect of nifedipine did not correlate with the serum drug concentration. The outcome of pregnancy was favourable in all cases.