A study of the disposition of alpha-methyldopa in newborn infants following its administration to the mother for the treatment of hypertension during pregnancy.

1 The nine infants participating in this study were born to mothers who received continuous therapy with alpha-methyldopa (0.75-2.0 g/day) for several weeks extending to the time of delivery. 2 The concentration of free and total (free plus conjugated) alpha-methyldopa was determined by gas chromatography-mass spectrometry in amniotic fluid, umbilical cord plasma and maternal plasma at delivery; also in urine collected over time intervals from neonates during the first days after birth. 3 The results indicate that alpha-methyldopa administered to the mother is present in the infant at birth at a level comparable to the maternal level and persists for some days. The ratio of conjugated to free drug increases with time after birth. 4 The excretion of free and conjugated alpha-methyldopa in the urine indicated that the drug is slowly eliminated in the neonate by excretion in the urine and apparently by metabolism, mainly to the sulphate conjugate. 5 The concentration of free and conjugated alpha-methyldopa in amniotic fluid tended to be higher than in umbilical cord plasma but lower than in neonatal urine, conjugated drug predominated.