Transfer of glyburide and glipizide into breast milk

OBJECTIVE - To determine if glyburide and glipizide are excreted into breast milk and if breast-feeding from women taking these drugs causes infant hypoglycemia. RESEARCH DESIGN AND METHODS - We studied eight women who had received a single oral dose of 5 or 10 mg glyburide. Drug concentrations were measured in maternal blood and milk for 8 h after the dose. In a separate study, five women were given a daily dosage (5 mg/day) of glyburide or glipizide, starting on the first postpartum day. Maternal blood and milk drug concentrations and infant blood glucose were measured 5-16 days after delivery. RESULTS - In the single-dose glyburide study, the mean maximum theoretical infant dose (MTID) as a percent of the weight-adjusted maternal dose (WAMD) was <1.5 and <0.7% for the 5- and 10-mg doses, respectively. For the five women taking daily dosages, the mean MTID as a percent of the WAMD was <28% for glyburide and <27% for glipizide. The high estimates were due to the insensitivity of the assay. Neither glyburide nor glipizide were detected in breast milk in either study and blood glucose was normal in the three infants (one glyburide and two glipizide) who were wholly breast-fed when the drug concentrations were at steady state. CONCLUSIONS - Neither glyburide nor glipizide were detected in breast milk, and hypoglycemia was not observed in the three nursing infants. Both agents, at the doses tested, appear to be compatible with breast-feeding.