Nifedipine pharmacokinetics during preterm labor

Citationsfrom the Literature and central venous pressures suggest central redistribution of intravascular volume if the generally accepted reports of decreased plasma volume in preeclampsia are correct.

Doppler assessment

of the fetal and uteroplacental

circulation

during nifedipine therapy for preterm labor

Mari G; Moise KJ Jr; Lee W; Cotton DB Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Baylor College of Medicine, One Baylor Plaza, USA AM J OBSTET GYNECOL 1989, 161/6 1(1514-1518) To investigate the effects of nifedipine on the human fetal circulation, 11 fetuses whose mothers were treated with nifedipine for treatment of preterm labor were studied. Maximum velocity waveforms were obtained in the middle cerebral artery (n = 8). renal artery (n = 6), ductus arteriosus (n = 8). and umbilical artery (n = 10). Transvalvular maximal velocity waveforms were obtained across the aortic (n = 11) and pulmonary (n = 7) valves. Maternal uterine arteries also were studied (n = 7). Doppler data were collected before and 5 hours after nifedipine therapy. Patients received an oral loading dose of 30 mg of nifedipine followed by a second oral dose of 20 mg 4 hours later. No significant difference in the flow velocity waveforms was found in the vessels studied 5 h after the initial dose. These results suggest that short-term nifedipine therapy does not influence either fetal or uteroplacental circulation as evaluated with the Doppler technique.

Nifedipine pbarmacokinetics

during preterm labor

Ferguson JE II; Schutz T; Pershe R; Stevenson DK Section of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, University School of Medicine, Stanford, CA, USA AM J OBSTET GYNECOL 1989,161/6 1(1485-1490) Nifedipine, a calcium entry blocker, has known relaxing effects of the myometrium. Thirteen women in preterm labor received nifedipine for tocolysis. Blood samples obtained serially during treatment and at the time of delivery were assayed for maternal and neonatal nifedipine concentrations. The peak concentration of nifedipine during sublingual therapy ranged from 23.4 to 197.9 ng/ml and reflected substantial interpatient variability. The mean (*SD) measurable trough value in patients who received 20 mg of nifedipine orally every 6 hours was 7.2 f 5.5 ng/ml. The maternal mean half-life of nifedipine was 81 min (range 49 to 137 minutes). At delivery, neonatal nifedipine levels were nondetectable in 6 of the 11 neonates available for study; in 5, values ranged from 29.5 to 1.8 ng/ml. From these results, we conclude that both sublingual and oral nifedipine treatment results in variable but usually measurable maternal plasma concentrations and that placental transfer of nifedipine occurs.

The effect of intravascular

transfusion

on umbilical

393

venous

pressure in anemic fetuses with and without hydrops

Weiner CP; Pelzer CD; Heilskov J; Wenstrom KD Fetal Diagnosis and Treatment Unit, Division of MaternalFetal Medicine, Department of Obstetrics and Gynecology, University of Iowa Hospitals and Clinics, Iowa City, IA 52242, USA AM J OBSTET GYNECOL 1989, 16116 1(1498-1501) Human fetal umbilical venous pressure was measured during 20 intravascular transfusions performed for treatment of hemolytic anemia. The mean (+ 1 SEM) gestational age at the time of transfusion was 29.3 f 1 weeks and the mean beginning hematocrit was 27% ? 2%. The mean volume of infused packed red blood cells (70% hematocrit) was 90.3 f 7 ml. The mean hematocrit at completion of the procedure was 48% + 1%. In nonhydropic fetuses umbilical venous pressure rose progressively from 6.7 f 1 mmHg at the start of transfusion to 10.9 f 1 mm Hg at the completion of transfusion (p < 0.002). However, most fetuses who began the infusion with a normal umbilical venous pressure ended the transfusion with a normal umbilical venous pressure (< 10 mmHg). Fetuses with immune hydrops (n = 2) had elevated umbilical venous pressure values before the initiation of transfusion therapy when compared with the first transfusion of nonhydropic fetuses (12.5 * 0.5 vs. 5.7 f 1 mmHg, p = 0.01). However, the umbilical venous pressure measurements declined into the normal range within 24 hours of the first transfusion; this normalization was too rapid to be explained by the reversal of liver hypertrophy or portal hypertension. There was no demonstrable relationship between the rise in umbilical venous pressure and either the gestational age, the volume transfused, or the rise in hematocrit. This study demonstrated: (1) In terms of the umbilical venous pressure, direct intravenous infusion of the human anemic fetus is well tolerated; (2) the elevated umbilical venous pressure associated with immune hydrops can correct rapidly with red blood cell replacement. Maternal and fetal blood flow velocity waveforms with preterm labor: Relationship to outcome

in patients

Brar HS; Medearis AL; DeVore CR; Platt LD Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, University of Southern California School of Medicine, USA AM J OBSTET GYNECOL 1989, 161/6 1(1519-1522) Elevated systolic/diastolic ratios obtained by umbilical and uterine velocimetry have been used to predict adverse pregnancy outcome. We performed pretherapy umbilical and uterine velocimetry by means of continuous-wave Doppler uhrasonography on 92 patients who came for treatment in preterm labor. Fourteen (15.2%) and 12 (13%) patients had elevated uterine (> 2.6) and umbilical (> 3.5) systolic/diastolic ratios, respectively, and 9 (9.8%) patients had both ratios elevated. Overall 17 (18.5%) patients had at least one abnormal systolic/diastolic ratio. Patients with abnormal Doppler waveforms had a significantly shorter gestation, infants with lower birth weights, and a higher incidence of adverse pregnancy outcome as determined by meconium, cesarean section Int J Gynecol Obstet 32