Pregnant and lactating women are two special populations that present unique challenges for conducting research. Many women of reproductive age group (15-5 year) may have chronic medical problems and use a variety of pharmaceutical products (e.g., drugs, vaccines, and other biologic therapies). In the U.S., 60 million women are of reproductive age (15-44) , and there are about four million births per year . The magnitude of major chronic conditions in women less than 45 years is significant. In this population, asthma affects 6,099,000 women; epilepsy affects 466,000; and hypertension affects 2,700,000 . The prevalence of these conditions among pregnant women are 7% for asthma, 0.6-1.0% for epilepsy, and 6% for hypertension . Thus, many women enter pregnancy with medical conditions that require ongoing or episodic treatment. New medical problems may develop or old ones may be exacerbated by pregnancy (e.g., infections, migraine headaches, depression). Lactating women, as well, may require medication for chronic or acute conditions.
Pregnant and lactating women are usually not part of the traditional drug development program. As a matter of fact, pregnant and lactating women are actively excluded from most clinical studies. If pregnancy does occur during a clinical study, treatment is discontinued and the patient is frequently dropped from the study. Consequently, at the time of initial marketing, except for products developed to treat conditions specific to pregnancy (e.g., tocolytic agents for preterm labor, treatment of preeclampsia), there are usually no data on the appropriate dosage and frequency of administration during pregnancy. The same situation may also be seen after years of marketing; data in product labels regarding pharmacokinetics and dose adjustments during pregnancy and lactation rarely provide more information than was available at the time of initial marketing.
Decisions can and should be made during drug development to study the kinetics of products in these subpopulations. If the drug is anticipated to be used by women of reproductive age, then developers should consider when and how to study pregnant and lactating women because the drug will be used by them once marketed. If a drug has a good maternal- and fetalsafety profile, studies can be performed in pregnancy. Pharmacokinetic/ pharmacodynamic (PK/PD) studies in pregnant and lactating women should be considered if the drug is prescribed in or used by pregnant and lactating women or pregnancy or lactation are likely to significantly alter the PK of a drug (e.g., effect of pregnancy on a drug that is renally eliminated). These studies are especially important if use of the drug would be required and not optional to treat maternal medical conditions. If there is no systemic exposure to the product, or the product is not used by women of childbearing age, during pregnancy, and lactation there may be no need to conduct PK/PD studies.
The medical literature provides information about drugs being used in pregnant and lactating women and should help investigators select products for further study. Information on human pregnancy and lactation exposures and experiences usually emerge during the postmarketing phase for pharmaceutical products. Postmarketing data that demonstrate fetal and maternal safety help reduce the obstacles to performing PK studies in pregnancy. Publications in the medical or lay press may describe use of a drug in pregnancy and medical specialty groups may publish position statements or clinical recommendations for specific drug therapy for clinical scenarios. Publications may describe safety or efficacy in lactating women, safety in the breast-fed child via exposure to drug in breast milk, case reports describing use of a drug in lactating women, and information from medical specialty groups (e.g., consensus documents or opinion papers). These sources can help with determining the research questions to be investigated, and will additionally be useful when designing a protocol and informed consent documents, and obtaining IRB approval.
Health care providers and their patients must make decisions about the use of medications during pregnancy and lactation with little to no data to guide them in decision-making. The ultimate goal of PK/PD studies in pregnant and lactating women should be to provide meaningful information for patients and their health care providers so that they can make informed decisions about drug use and appropriate dosing during pregnancy and lactation. Studying Pharmaceuticals in pregnancy and lactation requires special considerations including methodological design, data analysis, and ethical and regulatory considerations. When studies are performed in pregnant and lactating women, frequently the study utilizes only a few women. In addition, methodologies are often inadequate to draw substantial conclusions and have little influence on clinical prescribing scenarios.
This chapter will address considerations for investigators who recognize the importance of drug use in pregnant and lactating women, the need for data to assist prescribing, and despite the obstacles, choose to study pregnant and lactating women.
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