Placental transfer of chlorthalidone and its elimination in maternal milk.

A gas chromatographic method has been used to determine chlorthalidone in amniotic fluid, maternal and foetal blood at delivery, and in maternal milk and blood three days after delivery, following the administration of chlorthalidone to nine pregnant women suffering from toxaemia of pregnancy. Placental transfer of chlorthalidone and elimination in maternal milk have been shown and the implications of these factors are discussed. An explanation has been proposed for our observations that foetal blood levels of the drug are about 15% of those in maternal blood.