• EXCRETION OF DRUGS THROUGH BREAST MILK

Abstract

Breastfeeding is the optimal form of infant feeding for the first months of an infant’s life, and the majority of healthy women initiate breastfeeding after the birth of their infant. Although the majority of medications are considered to be compatible with breastfeeding, cases of significant infant toxicity exist, suggesting a case by case risk assessment to be made before the mother initiates breastfeeding or drug therapy. Unfortunately, current clinical risk assessment is often compromised by the paucity of data, as studies in breastfeeding women and their infants are ethically difficult to conduct. However, as our understanding on drug transfer mechanisms increases, it has become abundantly clear that carrier-mediated processes are involved with excretion of a number of drugs into milk. A common reason for the cessation of breastfeeding is the use of medication by the nursing mother and advice by her physician to stop nursing. Such advice may not be warranted. This information is important not only to protect nursing infants from untoward effects of maternal medication but also to allow effective pharmacologic treatment of breastfeeding mothers. The distribution of these drugs between the slightly more acidic breast milk and the relatively neutral plasma is consistent with their weakly basic, acidic, or relatively neutral properties. In general, the study shows that codeine and morphine milk concentrations are higher than, salicylic acid milk levels are much lower than, and phenacetin, caffeine, and acetaminophen milk concentrations are relatively similar to their respective plasma levels. It is projected, from estimated steady-state milk concentrations of the drugs and their metabolites studied, that very low percentages of the therapeutic dosages (less than 0.7%) would be excreted in mother's milk, too low an amount to be clinically significant to the infant. This article provides an overview of the benefits of breastfeeding, the effect of medication use during breastfeeding on maternal decisions and infant health, and factors determining infant exposure to medication through the breast milk.