Teratogenic Drugs: Reassessing the Risks

Each year, millions of women of child-bearing age are prescribed drugs that have the potential to cause birth defects, according to a study from the University of Pittsburgh and the University of California, San Francisco. During an estimated 11 million annual office visits, 11.7 million class D or class X medications were documented. Class D drugs may have benefits in pregnancy despite a risk to the fetus; class X drugs are contra-indicated in women who are or may become pregnant.

The most commonly prescribed teratogens were anxiolytic agents, anti-convulsants, antibiotics such as generic doxycycline (e.g., Vibramycin canadian, Pfizer), and statins. Fewer than 5% of the prescriptions were for isotretinoin drug.

White women were prescribed potentially teratogenic drugs more often, in part because they were also more likely to be prescribed anxiolytic agents. Women with public insurance were also more likely to receive potentially teratogenic drugs than those with private insurance. Physicians who identified themselves as the patient’s primary care provider were less likely to prescribe the drugs, according to their reporting.

The researchers advise engaging women in shared decision-making about contraception when class D or class X drugs are involved. Although approximately 20% of the visits at which a ter-atogenic medication was prescribed would be expected to have included concurrent counseling about contraceptives, only 6% of visits actually did. Indeed, the researchers found no significant difference in the rates of contraceptive counseling with use of low-risk drugs and the potential teratogens.

Not all teratogenic drugs are equally dangerous, they emphasize. Anticonvulsants are associated with structural deformities, and there is “growing evidence” of central nervous system anomalies with the use of statins. Tetracyclines, which can cause tooth discoloration, and benzodiazepines, which cross the placenta but are not associated with structural deformities, are lower on the scale of risk.