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Nifedipine pharmacokinetics during preterm labor tocolysis
J E Ferguson1, T Schutz, R Pershe
1Department of Gynecology and Obstetrics, Stanford University School of Medicine, California.
American Journal of Obstetrics and Gynecology
|December 1, 1989
Summary
Nifedipine effectively reduces uterine contractions in preterm labor, but its concentration in mothers and newborns varies significantly. This study measured nifedipine levels to assess its use in tocolysis.
Area of Science:
- Obstetrics and Gynecology
- Pharmacology
- Neonatal Medicine
Background:
- Nifedipine is a calcium channel blocker with known myometrial relaxant properties.
- Preterm labor necessitates effective tocolytic agents to prolong gestation.
Purpose of the Study:
- To quantify maternal and neonatal nifedipine concentrations during tocolysis for preterm labor.
- To assess the variability and placental transfer of nifedipine.
Main Methods:
- Thirteen women in preterm labor received nifedipine (sublingual or oral).
- Serial blood samples were collected from mothers and neonates.
- Nifedipine concentrations were measured using assays.
Main Results:
- Maternal nifedipine concentrations showed significant interpatient variability (peak 23.4-197.9 ng/ml).
- Mean maternal half-life was 81 minutes.
- Neonatal nifedipine levels were mostly undetectable, but measurable in 5 out of 11 neonates.
Conclusions:
- Both sublingual and oral nifedipine yield variable maternal plasma concentrations.
- Placental transfer of nifedipine occurs, though neonatal levels are often low.