Plasma and Milk Concentrations of Active Metabolite of Ethyl Loflazepate in Two Lactating Mothers and Their Breastfed Infants

Abstract

Breastfeeding is important for the mental and physical health of mothers and newborn babies. The amount of ethyl loflazepate, an antidepressant drug, excreted into breast milk is not well clarified. Here, we measured the plasma and breastmilk levels of ethyl loflazepate in two lactating women on the third day after delivery and their breastfed infants on the fourth day after birth. The metabolite in plasma and breastmilk was measured by liquid chromatography/mass spectrometry. The metabolite concentrations in the respective milks of case 1 were 35.1 ng/mL (relative infant dose was 2.3％) and the metabolite concentrations of case 2 were 35.0 ng/mL (relative infant dose was 3.9％). The metabolite concentrations in mothers’ and infants’ plasma of case 1 were 128.9 ng/mL (mother), 67.5 ng/mL (infant). The metabolite concentrations in mothers’ and infants’ plasma of case 2 were 99.9 ng/mL (mother), 28.2 ng/mL (infant). Adverse drug symptoms, such as respiratory disorder and drowsiness, were observed in the case 1 infant from immediately after birth to day 2 and in the case 2 infant from immediately after birth until discharge on day 8. The present case report can contribute to the pharmacotherapy in pregnant and postpartum women with depression.