The placental transfer and pharmacokinetics of atropine were studied in 44 healthy parturients undergoing caesarean section. The concentrations in the plasma were determined by a new radioimmunoassay after intravenous (n=32) or after intramuscular (n=12) administration of 0.01 mg/kg of atropine. A fast placental transfer with apparent foetal uptake of the drug was found after intravenous injection. There was also a difference in the umbilical vein and artery concentrations after intramuscular administration. The maternal pharmacokinetics of i.v. atropine obeyed and two-compartment open model with a fast distribution phase (mean ta1/2=1.02 min) and quite fast elimination (t1/2=2.56h). The total apparent volume of distribution was 1.01/kg and the total plasma clearance 6.36 ml/min/kg. The mean peak maternal plasma levels after i.m. atropine administration were found at 1.59 h and the mean calculated half-life of elimination was then 2.1 h. No atropine was found in the amniotic fluid.

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Eighty milligrams of propranolol or sotalol was administered orally to two groups of 8 parturients who were to undergo elective cesarean section. This was performed 3 hours after drug administration. The transplacental passage of both drugs was registered in each patient. The maternal concentration of propranolol was approximately four times that in the umbilical circulation, while the sotalol level in maternal circulation was twice that in the umbilical circulation. The administration of beta-adrenoceptor antagonists caused a significant decrease in maternal plasma renin activity. After these doses of beta blockers, no difference in the plasma renin activity was found in the umbilical circulation, when compared with the previous normal values at cesarean section.

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