Low Levels of Amlodipine in Breast Milk and Plasma

Few clinical reports have addressed the use of the antihypertensive drug amlodipine during breastfeeding. The objective of this study is to characterize concentration-time profiles of amlodipine in maternal and infant plasma, and milk.Plasma and breast milk samples were obtained from eight nursing mothers and their nine newborn nursing infants (median postnatal age: 6.5 days, range 5-7 days). Participants were recruited from February 2009 to June 2009. Multiple blood and milk samples were obtained from the mothers over a 24 hours dosing interval. The blood of infants was also obtained at before and 8 hours after nursing. Amlodipine concentrations were determined by high-performance liquid chromatography. Relative infant dose (RID) was calculated by dividing the infant's dose via milk in mg/kg/day by the maternal dose in mg/kg/day, assuming that a daily intake of milk is 150 mL/kg/day in the infants.Maximal amlodipine concentrations in mothers ranged from 4.4 to 14.7 ng/mL in plasma, and 6.5 to 19.7 ng/mL in milk (Average milk/plasma ratio: 1.4). RID was 3.4% of the maternal weight-adjusted dose. All plasma concentrations in infants were under the quantitation limit (0.4 ng/mL).Infant exposure to amlodipine in breast milk appears very small, suggesting that amlodipine can be used with little influence on infants during breastfeeding.