Breast-feeding and maternal drug use.

Because drugs are almost never tested for use in lactating women before marketing, uncertainties about their safety for breast-fed infants often cause anxiety and unnecessary interruption of breast-feeding. Based on an understanding of mechanisms and principles of drug excretion into milk, we can rationally minimize the uncertainties. As described in this article, the infant exposure levels may be predicted using actual data on drug concentrations or even theoretic equations. Although the approach has to be rigorously tested in future studies, informed decisions on breast-feeding during maternal drug therapy are now within reach of resourceful health professionals. As more outcome data become available, remaining uncertainties will be addressed.