Sotalol, a beta-adrenoceptor blocking drug, was administered to 12 hypertensive pregnant women. The concentration of the drug was assayed in samples of maternal plasma, amniotic fluid and mixed umbilical cord plasma at delivery and, in five mothers who elected to breast feed, in paired samples of maternal plasma and breast milk. Sotalol reduced blood pressure effectively at a mean daily dose of 433.1 & 54 * 1 mg but crossed the placental barrier. The mean maternal: fetal plasma concentration ratio was 1 : 1.05 and the mean amniotic fluid concentration was 7 * 0 & 2 * 7 pg/ml. Delivery occurred at mean gestational age of 37 * 7 I 0 * 7 weeks ; 12 infants were liveborn with a mean weight of 2 . 8 k O . l kg and eight of them had no significant neonatal problems. Of the other four, two died from severe congenital anomalies, one had perinatal asphyxia and one mild transient hypoglycaemia. High sotalol concentrations were found in breast milk (mean plasma : milk ratio was 1 : 5 -4) raising the possibility of pharmacological effect in the newborn infant. The results suggest that sotalol adequately controls blood pressure in hypertension complicating pregnancy but because, unlike results from the pregnant ewe, it crosses the human placental barrier it offers no apparent advantages over other beta-adrenoceptor antagonists.
Propranolol, a beta-adrenoceptor blocking drug, was administered to 6 healthy pregnant volunteers between 32 and 36 weeks gestation and when at least 6 weeks postpartum. On both occasions, subjects were given propranolol 120 mg orally or 10 mg intravenously in randomised order with a minimum washout period of 1 week. Propranolol was assayed in plasma by gas-liquid chromatography with electron-capture detection and the pharmacokinetic parameters were investigated. There were no significant alterations in elimination half-life, clearance or apparent volume of distribution per kilogram antenatally compared with postnatally: bioavailability was also unchanged. It is concluded that the disposition of propranolol is not altered during pregnancy.
Sotalol, a beta-adrenoceptor blocking drug, was administered to 6 healthy pregnant volunteers between 32-36 weeks gestation and when at least 6 weeks post-partum. On both occasions, each volunteer was given sotalol 100 mg intravenously and 400 mg orally in randomised order with at least a 1 week washout period between. Plasma samples were analysed for sotalol using a fluorometric method and the pharmacokinetic profiles investigated. The systemic clearance of sotalol was significantly greater in the antenatal period (2.4 +/- 0.3 ml/min/kg) than in the post-natal phase (1.5 +/- 0.1 ml/min/kg). The apparent volume of distribution was similar in the two periods: the elimination half-life was 6.6 +/- 0.6 h ante-natally and 9.3 +/- 0.7 h post-natally after intravenous drug but the trend for faster elimination was not significant. The elimination half-life after oral administration (about 10 h) and bioavailability (about 90%) were not altered significantly by pregnancy. It is suggested that the more rapid clearance of sotalol in pregnancy may be due to increases in renal plasma flow and glomerular filtration rate.
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