Drugs of Choice in Pregnancy

Many pregnant women require drug therapy because of pregnancy-induced conditions such as nausea and vomiting, chronic conditions diagnosed before pregnancy, or acute conditions (e.g., those that require surgical treatment with the use of anesthetic agents).

Several principles should guide the selection of therapy during pregnancy. Since fetal safety is a major concern, effective drugs that have been in use for long periods are preferable to newer alternatives. Table 5 -  Selected Drugs That Can Be Used Safely during Pregnancy, According to Condition lists selected drugs considered to be safe on the basis of either single large cohort studies or meta-analyses of several studies. Newer drugs may be more specific or have fewer adverse effects in adults, but their safety for fetuses is less likely to be known. For example, although acetaminophen with or without codeine may not be effective in many patients with migraine, it is widely used during pregnancy. Other, more potent antimigraine drugs are either too new (e.g., sumatriptan) or have known reproductive risks (e.g., ergotamine alkaloids that cause uterine contraction).

To minimize the fetal risk, drug doses at the lower end of the therapeutic range should be prescribed during pregnancy. However, because of increased body weight and more rapid clearance of many drugs (e.g., lithium, digoxin, and phenytoin) during late pregnancy, some women may need higher-than-normal doses.

Pregnant women should be discouraged from taking over-the-counter drugs, and such drugs should not be taken without counseling, since many factors, including the stage of pregnancy, can influence the risk to the fetus. For example, a nonsteroidal antiinflammatory drug may be taken safely for pain during the first trimester of pregnancy, but there is increasing evidence that some nonsteroidal antiinflammatory drugs constrict or even close the fetal ductus arteriosus during late pregnancy.

Conclusions

In addition to the risk associated with fetal exposure to teratogenic drugs, there is a risk associated with misinformation about the teratogenicity of drugs, which can lead to unnecessary abortions or the avoidance of needed therapy. The medical community and drug manufacturers should make a concerted effort to protect women and their unborn babies from both risks.

Supported by grants from the Medical Research Council of Canada, the National Health and Welfare Research Program, the Medical Research Council–Pharmaceutical Manufacturers Association of Canada Program, Physicians Services, Novartis, Roche Canada, Duchesnay, and the Motherisk Research Fund.