Topical application of a drug can lead to systemic absorption, and the magnitude by which this occurs can be affected by numerous factors (see Chap. 1 ), potentially leading to systemic effects and toxicity. Some of the considerations include issues related to pregnancy, lactation, renal dysfunction, hepatic dysfunction, potential drug interactions, and altered physiologic states. This chapter will review each of the italicized considerations and the potential pharmacologic and adverse effects of various drugs when applied topically in these specific conditions. Some dermatologic conditions seen in pregnancy are also discussed.