Use is not recommended unless clearly needed.

AU TGA pregnancy category: C
US FDA pregnancy category: B

Comments:
-Insulin is recommended during pregnancy to maintain blood glucose levels as normal as possible.
-If this drug is used during pregnancy, it should be discontinued at least 2 weeks before the expected delivery date.

Abnormal blood glucose levels during pregnancy are associated with a higher incidence of congenital abnormalities. Reproductive studies in rats and rabbits at doses up to 500 times the human glyburide dose have not revealed evidence of harm to the fetus. Neonates born to mothers receiving a sulfonylurea at the time of delivery have experienced prolonged severe hypoglycemia, especially with use of agents that have prolonged half-lives. Sulfonylureas may not be suitable for the treatment of diabetes during pregnancy as significant metabolic changes occurring during this time make control of blood sugar difficult. Metformin itself was not teratogenic in rats or rabbits at doses up to 600 mg/kg/day. There are no adequate and well-controlled studies in pregnant women.

In the US, glyburide has been used in women with gestational diabetes. A retrospective cohort study looking at employer-based insurance claims suggests newborns born to mothers receiving glyburide were more likely to experience adverse reactions than those born to mothers receiving insulin. Of the 110,879 women identified with gestational diabetes mellitus, 4982 women were treated with glyburide and 4191 received insulin. Newborns of mothers treated with glyburide were at an increased risk for neonatal intensive care unit admission, respiratory distress, hypoglycemia, birth injury, and large for gestational age. They were not at increased risk for obstetric trauma, preterm birth, or jaundice; the risk of cesarean delivery was 3% lower. Additional studies are needed to fully assess the risks of this drug during pregnancy.

AU TGA pregnancy category C: Drugs which, owing to their pharmacological effects, have caused or may be suspected of causing, harmful effects on the human fetus or neonate without causing malformations. These effects may be reversible. Accompanying texts should be consulted for further details.

US FDA pregnancy category B: Animal reproduction studies have failed to demonstrate a risk to the fetus and there are no adequate and well-controlled studies in pregnant women.

See references

Both glyburide and metformin are found in low levels in human milk. In a small (n=8) single-dose study, maximum estimated glyburide doses expected in fully breastfed infants would be less than 1.5% and less than 0.7% of the maternal weight-adjusted dose for the 5 and 10 mg doses, respectively. Metformin drug levels are expected to be 0.5% of their mother's weight-adjusted dosage and are expected to be relatively constant. A large study in mothers receiving metformin found no adverse effects in their breastfed infants; there were low detectable serum levels in some infants. Monitoring of the breastfed infant's blood glucose is advisable during maternal therapy with hypoglycemic agents.

Use is not recommended and a decision should be made to discontinue breastfeeding or discontinue the drug, taking into account the importance of the drug to the mother.

Excreted into human milk: Yes (glyburide); Yes (metformin)

Comments: If diet alone is inadequate for controlling blood glucose, insulin therapy should be considered.

See references