2 - Effects of drugs on milk secretion and composition

Abstract

Drugs can potentially effect lactation by intervening at all stages in the development and function of the mammary gland. In particular, drugs may interfere with the following processes: normal mammary gland development, milk secretion, the hormonal milieu of the lactating mammary gland, and nutrient delivery to the lactating mammary cell. The rate of milk secretion or milk composition can be potentially altered by agents that act in a number of ways: the agents may act directly on the mammary epithelium affecting its growth or its function; the agents may affect the hormonal milieu that regulates milk secretion or ejection; or the agents may alter the delivery of nutrients to the lactating mammary cell. After a brief review of mammary development and the mechanisms of milk secretion, this chapter discusses the potential effects of drugs on mammary development, focusing on anti-estrogens. During lactation, a large number of drugs act through the dopamine receptor on the lactotroph to increase or decrease prolactin secretion. Alcohol and opioids inhibit oxytocin release, interfering with the let-down reflex. A great deal of information is available about the effects of sex steroids on milk secretion from studies of oral contraceptive agents. In general, estrogens, particularly at high doses, inhibit milk secretion whereas progesterone appears to have little effect. Other points where drugs might be expected to act are the secretory architecture of the mammary secretory cell and the enzymes of lipid synthesis.