DRUGS, PREGNANCY, AND LOCATION.

Common Misperceptions About Drug Safety

OB.GYN. NEWS is pleased to welcome a new contributor to Drugs, Pregnancy and Lactation, Dr. Gideon Koren, who is professor of pediatrics, pharmacology pharmacy, medicine, and medical genetics at the University of Toronto. He is also director of the Motherisk Program in the division of clinical pharmacology and toxicology at the Hospital for Sick Children in Toronto. The program conducts research and provides information and counseling to women and health care providers on drug therapy during pregnancy.

The science of both risk assessment and clinical pharmacology have progressed, but unfortunately many of the findings have not been incorporated into clinical practice. This is especially true with drug use in pregnancy and lactation. We at the Motherisk program field as many as 200 inquiries per day from women and health care professionals, and it is evident that they have several misperceptions about drug safety in pregnant and lactating women.

For example, many physicians won't prescribe corticosteroids during the second and third trimesters, because they are misinformed about drug risk. It is true that when asthma is treated with corticosteroids, there is about a three-fold increased risk of orofacial clefts. But the palate has already fused by 8-10 weeks' gestation, and there is no way that corticosteroids can cause this malformation in the second and third trimester.

Similarly, many physicians don't prescribe lithium in the second and third trimesters because they are afraid of the risk of Ebstein's anomaly. This condition, however, is associated only with first-trimester use.

With lithium, the increase in risk of Ebstein's anomaly is pretty much proven. But the background rate in the general population is 1 in 20,000 births; with lithium exposure in the first trimester, the rate may increase to 1 in 5,000 births. We did a prospective study of 150 pregnant women who were taking lithium and identified one case of Ebstein's. Most women who need lithium find it reassuring when we tell them that 149 of these women did not have a baby with this anomaly.

Misinformation has even led to the removal from the U.S. market of Bendectin (doxylamine-pyridoxine), a safe drug used to treat nausea and vomiting in pregnancy. There was a threefold increase in women ...