Glyburide's PK and PD have not been studied in women with gestational diabetes mellitus (GDM). The objective was to assess steady-state PK of glyburide as well as insulin sensitivity, beta-cell responsivity and overall disposition indices following a mixed meal tolerance test (MMTT) in GDM (n=40), non-pregnant type 2 diabetic (T2DM) (n=26) and healthy pregnant (n=40, MMTT only) women. At equivalent doses, glyburide plasma concentrations were ~50% lower in pregnancy compared to non-pregnant women. Average glyburide umbilical cord to maternal plasma concentration ratio at the time of delivery was 0.7 ± 0.4. Insulin sensitivity was ~5-fold lower in women with GDM compared to healthy pregnancy. Despite comparable beta-cell responsivity index, average beta-cell function corrected for insulin resistance was >3.5-fold lower in women with glyburide-treated GDM than healthy pregnancy. Women with GDM that fail glyburide may benefit from alternate medication selection or dosage escalation, though fetal safety should be considered.Corresponding Author and Reprint Requests: Mary F. Hebert, Pharm.D., FCCP, University of Washington, Department of Pharmacy, 1959 NE Pacific St., H-375 Health Science Center, Box 357630, Seattle WA 98195-7630, Phone: 206-616-5016, Fax: 206-543-3835, Email: E-mail: mhebert@u.washington.edu. * Current address: Pfizer Global Research and Development, San Diego CA CONFLICT OF INTEREST/DISCLOSURE At the time of study conduct and analysis, the authors declare no conflict of interest. However, since completion of the study, Dr. Vicini's affiliation has become Pfizer Global Research and Development. NIH Public Access Author ManuscriptClin Pharmacol Ther. Author manuscript; available in PMC 2010 June 1. Published in final edited form as:Clin Pharmacol Ther. Gestational diabetes mellitus (GDM) complicates 5-12% of pregnancies and is associated with adverse pregnancy outcomes. Insulin has been the mainstay of pharmacotherapy for GDM. Glyburide's (GLY) advantages include easier route of administration and schedule as well as improved patient satisfaction and adherence. GLY's acceptance has been due to its comparable efficacy with insulin and limited transfer to the fetus.(1,2) However, the pharmacokinetics (PK) of GLY have not been studied in pregnancy and dosage strategies generally follow those used in non-pregnant patients with type 2 diabetes mellitus (T2DM). We hypothesized that the PK of GLY would be different during pregnancy, due to the expected changes in metabolism, protein binding, and body composition. In addition, the effects of GLY on the insulin sensitivity and secretion parameters have not been systematically studied. Our objectives were to compare GLY PK in women with GDM and non-pregnant T2DM, to measure fetal exposure to glyburide at delivery and to evaluate insulin sensitivity (SI), beta-cell responsivity index (Φ total ) and disposition index (DI) following a mixed meal tolerance test (MMTT) in women with GDM on GLY therapy, compared with gestational age-matched healthy pregnant ...