SAN FRANCISCO – Because of significant limitations in the Food and Drug Administration’s pregnancy categories, it’s important to have another reliable resource handy to guide prescribing during pregnancy, Dr. Elizabeth S. Harleman believes.
Three out of four attendees at a conference on women’s health sponsored by the University of California, San Francisco, said that they use the FDA categories to determine a drug’s safety during pregnancy, an informal electronic poll at the meeting showed. There are good reasons for that, Dr. Harleman told the audience. The FDA categories are easily accessible, quick to read, and provide some information.
Dr. Elizabeth S. Harleman
But they’re also hard to remember and don’t provide sufficient information, she added. "I think it’s going to become increasingly important, as we take care of more women with chronic diseases earlier in life, to think about the implications of conceiving while on the medications that we’re prescribing," said Dr. Harleman, of the department of medicine at the university.
The FDA categories do not provide any gradation of risk. Drugs in the A or B categories are not necessarily safer than category D drugs, she said. A medication can get a B categorization without any human data. The FDA categories give no information about dosing or the timing of administration. "If you give a drug in the first trimester, there may be very different implications than if you give a drug in the third trimester, and you can’t get that information from this classification system," she said.
There’s also no information on the change in risk from one category to another. "We don’t know if this increases the risk from 1% to 5% or from 1% to 80%," Dr. Harleman said. "It’s very hard to make an informed decision about prescribing a medication just using the FDA classification."
Approximately 60% of drugs in category X have no human data behind that classification. A drug can end up in category X simply because it has no utility during pregnancy, such as oral contraceptives. Physicians who don’t know that, however, may erroneously tell a woman who conceived while on an oral contraceptive that the drug increases her baby’s risk for malformation.
The FDA categories rarely get updated. "It’s really more of a legal system" than a helpful clinical tool, she said.
Half of pregnant women who are on medications take category C, D, or X drugs, studies have shown. One in six women of reproductive age receives a category D or X drug, mainly antibiotics, anticonvulsants, statins, benzodiazepines, or warfarin. A study of 488,175 women found that those taking category D or X drugs were no more likely to have documentation in their physicians’ charts of a discussion about contraception.
"In our hurried practices, sometimes it’s hard to remember this, but we need to think about which drugs are absolutely contraindicated and make sure that we are discussing them with our patients," Dr. Harleman said.
The main drugs to avoid during pregnancy are ACE inhibitors, tetracycline, fluoroquinolones, systemic retinoids, warfarin, valproic acid, nonsteroidal anti-inflammatory drugs, and live vaccines. "It’s a pretty short list," she said. "A lot of other drugs are safe in pregnancy; we may just not have as much familiarity with using them."
Dr. Harleman gave three pieces of advice on prescribing during pregnancy: Think hard before starting or stopping any medication. Remember that changes in blood volume and metabolism during pregnancy may mandate increased frequency of dosing or higher doses. And keep one of the following pregnancy prescribing resources available instead of relying solely on the FDA categories:
• The clinical reference tool Micromedex. It has an excellent "ReproRisk" section, she said (micromedex.com).
• Reprotox, a service of the nonprofit Reproductive Toxicology Center, Washington. It synthesizes all the published information on drug safety and provides quick-take summaries that Dr. Harleman believes are worth the low fee for use (reprotox.org/Default.aspx).
• The American College of Physicians’ "Medical Care of the Pregnant Patient," 2nd ed. (Hanover, Pa.: Sheridan Press, 2008) is a good source.
• Motherisk is a service affiliated with the Hospital for Sick Children, Toronto (motherisk.org).
• MotherToBaby is a service of the Organization of Teratology Information Specialists (mothertobaby.org).
• The reference guide "Drugs in Pregnancy and Lactation: A Reference Guide to Fetal and Neonatal Risk," 9th ed. (Philadelphia: Lippincott Williams and Wilkins, 2011) is a good source.
• The book "Medications and Mother’s Milk" (Amarillo, Tex.: Hale Publishing, 2012) is helpful.
Dr. Harleman reported having no financial disclosures.
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