Drug Therapy in Pregnancy and Lactation

The use of drugs in pregnant and lactating women requires a thorough understanding of the unique interactions between the mother, fetus/infant, and the pharmacologic agents that are used in therapy. Any agent that is consumed by a woman may have adverse effects on the fetus/infant. This article will summarize those factors that should be considered. There exists a paucity of data and information for most drugs relative to pregnancy and lactation. Conclusions that can be drawn remain speculative, and the use of any drug during pregnancy and lactation requires extreme caution. Factors involved in fetal drug exposure include the dynamic changes of maternal physiology related to drug absorption, distribution, metabolism, and excretion. Placental transfer of drug occurs with almost all agents, each to varying degrees. The notion that the placenta provides an impervious barrier must be dismissed. The least understood of factors involving potential fetal harm is teratogenicity. The mechanisms and types of teratogenic agents, poorly understood in humans, is discussed. Most drugs appear in the breast milk and, therefore, carry some degree of potential harm. Minimizing exposure is a goal that can be obtained when taking into account the maternal physiology, basic pharmacokinetic factors, physiochemical interactions between drug and membranes, and the chemical composition of breast milk.