Maternal-fetal transport of hypoglycaemic drugs

Due to legal, ethical and monetary problems, drug studies in pregnancy are rare. Numerous pharmacokinetic and pharmacodynamic changes occur in pregnancy that can affect the efficacy and safety of drugs, and these are difficult to predict without appropriate studies. Drugs potentially useful and safe in pregnancy have to either not cross the placenta and/or be harmless to the fetus at clinically relevant concentrations. The first characteristic can be predicted using in vitro models such as the placenta perfusion model. In the case of glibenclamide (glyburide), in vitro experiments showed minimal maternal-fetal transfer, leading to completion of a successful clinical trial of this drug in gestational diabetes. Insulin, the main drug used in diabetes during pregnancy, has also been shown not to cross the placenta in vitro, as has insulin lispro. Animal insulin may cross the placenta when complexed with anti-insulin antibodies. Other sulphonylurea drugs (tolbutamide and chlorpropamide) have been shown to cross the placenta both in vitro and in vivo and to produce toxicity in the fetus. This review summarises the pharmacokinetic data available for hypoglycaemic drugs during pregnancy, as well as the potential role for the in vitro placenta perfusion model in the preclinical evaluation of drugs with potential usefulness in pregnancy.