Medications in the Breast-Feeding Mother -- American Family Physician

www.aafp.org/afp AMERICAN FAMILY PHYSICIAN 119 largely determined by the maternal serum drug concentration. This serum concentration tends to be lower with medications that have large volumes of distribution and fluctuates more with medications that have short half-lives. Retrograde diffusion of the drug from breast milk to plasma may remove a medication from the milk even if the mother has not emptied her breasts. Medications that are highly protein bound, that have large molecular weights or that are poorly lipid-soluble tend not to enter the breast milk in clinically important quantities. In the early postpartum period, large gaps between the mammary alveolar cells allow many medications to pass through this milk that may not be able to enter mature milk. These gaps close by the second week of lactation. The nursing infant’s drug exposure depends on the drug’s concentration in the breast milk and the amount of breast milk consumed by the infant. The pharmacologic activity of the medication depends on its absorption, distribution, metabolism and elimination by the infant. Table 1 lists ways to minimize the risk of toxicity to infants from maternal medications.