Pharmacokinetics of terbutaline during pregnancy.
Terbutaline in plasma was determined in three groups of women by gas chromatography-mass spectrometry. Eight women received a single i.v. dose of 0.25 mg terbutaline sulphate during pregnancy and 3-6 months after delivery. Mean plasma clearance was 29% higher during pregnancy than after delivery. There was a subsequent decrease in mean terminal half-life from 5.3 to 3.7 h and in mean residence time from 5.3 to 3.4 h. There was no change in volume of distribution. A second group of pregnant women in premature labour (n = 8) received oral terbutaline 5 mg t.d.s. The dosing was repeated after delivery. The mean steady state plasma concentration of terbutaline was about 30% lower during pregnancy than after delivery. A third group of women in preterm labour (n = 8) was treated with an i.v. infusion of terbutaline. The concentrations of terbutaline found on cessation of uterine contractions ranged between 12.8 and 31.5 ng/ml. At present there is no basis for formulation of a "therapeutic plasma level" of terbutaline for the treatment of preterm labour.
D000284:Administration, Oral; D000328:Adult; D005260:Female; D005318:Fetal Heart / Q000187:drug effects; D006207:Half-Life; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D007275:Injections, Intravenous; D007700:Kinetics; D007752:Obstetric Labor, Premature / Q000517:prevention & control; D011247:Pregnancy; D013726:Terbutaline / Q000008:administration & dosage / Q000009:adverse effects / Q000378:metabolism*; D014590:Uterine Contraction / Q000187:drug effects
D013726:Terbutaline