Amlodipine Passage into Breast Milk in Lactating Women with Pregnancy-Induced Hypertension and Its Estimation of Infant Risk for Breastfeeding

Abstract

Background: Few clinical reports have been published on amlodipine passage into breast milk in lactating women. Objectives: The aims of this study were to evaluate the plasma concentration of amlodipine and its passage into breast milk in lactating women with pregnancy-induced hypertension and to estimate the risk for breastfeeding infants. Methods: Thirty-one lactating women receiving oral amlodipine once daily for pregnancy-induced hypertension were enrolled. Pre-dose plasma and milk concentrations of amlodipine were determined at day 6 or later after starting the medication. Relative infant dose (RID) as an infant risk for breastfeeding was calculated by dividing the infant dose via milk by the maternal dose. Results: The mean maternal dose of amlodipine was 6.0 mg. The medians of the plasma and milk concentrations of amlodipine were 15.5 and 11.5 ng/mL, respectively. Interindividual variation was observed in the amlodipine dose and body weight–adjusted milk concentrations (interquartile range [IQR], 96.7-205 ng/mL per mg/kg). The median and IQR of the amlodipine concentration ratio of milk to plasma were 0.85 and 0.74 to 1.08, respectively. The medians of infant birth weight and daily amlodipine dose via milk were 2170 g and 4.2 μg/kg, respectively. The median of the RID of amlodipine was 4.2% (IQR, 3.1%-7.3%). Conclusion: Lactating women with pregnancy-induced hypertension had higher plasma concentrations of amlodipine during the early postpartum period. Oral amlodipine transferred into breast milk at the same level as that of plasma. However, the RID of amlodipine in most patients was less than 10%.