Background: This article describes the principles of drug transfer into breast milk and how drugs may affect breast-fed infants, and provides practical advice about what should be considered when prescribing medication for a lactating woman.
Material and method: The article is a review based on a discretionary selection of articles found after a search in PubMed, recommendations from Norwegian and international expert groups, and the authors' own studies and experience.
Results: Recommendations concerning the use of drugs among breast-feeding women tend to be based on studies in which the degree of drug transfer to the mother's milk has been measured or on case studies, sometimes in combination with pharmacokinetic or pharmacodynamic considerations. The toxicity and dosage of the medication, duration of treatment, as well as the infant's age and health condition need to be considered. Psychotropic drugs are the drug group for which most studies have been published. This is also the group for which individual risk/benefit evaluations are most often required, since a risk of pharmacological effects on the infant cannot be excluded.
Interpretation: Most drugs can be used by breast-feeding women, since the amount transferred to the breast milk is too small to have any pharmacological effects on the infant. In most cases, the sum of available information in combination with clinical experience will be sufficient to provide specific advice about the use of medication during breast-feeding.