Emerging Research Paradigm for Infant Drug Exposure Through Breast Milk

Background: Information on drug secretion into milk is insufficient due to the exclusion of lactating women from clinical trials and drug development processes. As a result, non-adherence to the necessary drug therapy and discontinuation of breastfeeding occur, even if the predicted level of infant exposure is low. In contrast, inadvertent infant exposure to drugs in breast milk continues to happen due to lack of rational risk assessment, resulting in serious toxicity cases including death. This problem is multifactorial, but one of the key elements is the lack of pharmacokinetic information on drug secretion into milk and resultant infant exposure levels, the first line of evidence for risk assessment. Methods: Basic PK principles in drug excretion into milk were explained. The literature was scanned to identify approaches for PK data acquisition in this challenging field. Results: This review describes the feasibility to develop such approaches, and the knowledge gaps that still exist. A combination of population pharmacokinetics approach (to estimate averages and variations of drug concentration profiles in milk) and physiologically-based pharmacokinetics modeling of infants (to predict the population profiles of infant drug exposure levels) appears useful. Conclusions: In order to facilitate participant enrollment and PK data acquisition in a timely manner, networks of investigators become crucial.