Medications and breastfeeding

Breastfeeding mums can safely use most prescribed medications. It is well known that most medications transfer into milk to an extent, however, most do so in levels which are not hazardous to the baby. Nonetheless, doctors and pharmacists should be notified that a mother is breastfeeding prior to prescribing her a particular medication.

Drugs may transfer into milk if they reach high concentrations in maternal plasma, are low in molecular weight (<800 Da), are low in protein binding and pass easily into the brain. Other factors, such as the oral bioavailability of the medication to the baby, are also very important. Many medications, for instance, can be destroyed in the baby’s gut or are stored in the mother’s liver, and may never reach the mother’s plasma.

Drugs can enter milk by passive diffusion from the maternal plasma compartment and the maternal milk compartment. Medications normally pass from maternal plasma into the lactocytes, but they must pass through both bilayer lipid membranes of the lactocytes to reach the milk. During the first three days post-partum, however, tight junctions between lactocytes can be open and permit enhanced drug transfer into the milk.