Maternal‐to‐Infant Transfer of Medications for Type 2 Diabetes Mellitus Via Breastmilk: A Systematic Review of Available Evidence and Clinical Guidelines

This review evaluates the available pharmacokinetic data on the plasma-to-breastmilk transfer of first- and second-line T2DM drugs against available clinical guideline recommendations. A list of drug therapies for treating T2DM was generated from national and international clinical guidelines. A systematic search of research articles reporting human plasma and breastmilk drug concentrations was conducted in Scopus, PubMed, Google Scholar, and LactMed® in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Studies evaluating breastmilk drug transfer in T2DM, with fully accessible abstract and main text reported in English, were included. Study quality was evaluated using the ClinPK checklist. Authors evaluated clinical guideline recommendations on the use of T2DM drugs in lactation and the basis upon which such recommendations were made. Only 5 out of 20 drugs (metformin, glyburide, glipizide, tolbutamide, and semaglutide) have clinical data on plasma-to-breastmilk transfer. Metformin and tolbutamide were detectable in maternal plasma and breastmilk. Half (51.7%) of guideline recommendations provide explicit guidance. Only 4.4% of recommendations were based on clinical evidence. Over half (57.8%) of recommendations were accessible online, and most guideline recommendations (78%) were against the use of antiglycemic agents while breastfeeding. The scarce clinical evidence to guide T2DM drug therapy during breastfeeding available has several design and methodological limitations. Published recommendations remain largely inconsistent, thus perpetuating uncertainty in the use of T2DM drug therapies in lactation. Addressing knowledge gaps is critical in developing clinical consensus to optimize T2DM drug therapy among breastfeeding mothers.