Drug Safety During Breastfeeding: A Comparative Analysis of FDA Adverse Event Reports and LactMed®

Background: While breastfeeding is highly recommended, breastfed infants may be exposed to drugs by milk due to the mother’s medication, with a risk of adverse drug events (ADE) or reactions (ADRs). The U.S. Food and Drug Administration (FDA) Adverse Event Reporting System (FAERS) is an online pharmacovigilance database, while the Drugs and Lactation Database (LactMed®) includes information on the levels of such substances in breast milk and infant blood, and the possible adverse effects in the nursing infants. Methods: The FAERS database was explored (July 29, 2024) on ADEs related to exposure during lactation, while annual trends, outcomes, and region of reporting were determined. Active pharmaceutical ingredients (API) were categorized based on Anatomical Therapeutic Chemical (ATC) classification. The top 5 APIs in each first level of ATC system were explored on ADEs reported and compared to LactMed®. Results: 2628 ADEs were obtained from the FAERS database, with increased reporting over time, while most ADEs were from North America (44.9%). Most drugs (50.9%) were nervous system drugs. The most frequent outcome was "other outcomes" (58.2%). 84,7% of the cases were categorized as serious. Related to the same drug, the FAERS database and LactMed® exhibited similarities and differences in adverse events, possibly due to factors such as maternal and neonatal pharmacokinetics (PKs), maternal therapy and infant exposure durations, milk production, and infant’s daily milk volume intake or causality assessment. Conclusions: ADE reporting systems are useful for obtaining information about medication related ADEs during lactation to increase knowledge on medication safety and awareness for possible risks in infants. The FAERS should be perceived a useful tool to detect ADEs, be it without ADR assessment.