If the mother requires a drug that poses a risk for her infant for only a short time, she can pump her breasts to maintain lactation and discard the milk. This applies to diagnostic radiopharmaceuticals, antiprotozoal compounds, and a few antibiotics that cannot be safely given to an infant (such as chloramphenicol). Compounds such as sulfadiazine may be contraindicated for the breastfeeding mother in the early postpartum period but are well tolerated when the infant is at least 1 month of age. Certain other drugs are contraindicated during breastfeeding. They include antineoplastic drugs, therapeutic radiopharmaceuticals, lithium, lactation-suppressing drugs, certain antithyroid drugs, and synthetic anticoagulants (for specific information, see Briggs et al. , Committee on Drugs , and Lawrence ).
The use of caffeine to treat immature infants with apnea has provided an opportunity to study the absorption, distribution, metabolism, and excretion of this drug in neonates. The milk-to-plasma ratio ranges between 0.5 and 0.8—an amount less than 1% of the maternal dose. However, when an infant receives frequent doses, caffeine can accumulate, causing wakefulness or irritability. Maternal consumption of one or two caffeine-containing beverages per day is not associated with unacceptable levels of caffeine in human milk (Committee on Drugs, 1989; Wilson, 1981; Wilson et al., 1985).
There is evidence from a study in Costa Rica that maternal consumption of three or more cups of coffee per day during pregnancy and lactation can affect iron concentrations in milk and infant iron status at 1 month of age (Muñoz et al., 1988). Studies in rats suggest that this effect is not due to caffeine but to some other component(s) in coffee (Muñoz et al., 1986). There is a need for further investigations in other populations and in pregnant and lactating women consuming fewer than three cups of coffee per day.
Small amounts of alcohol have been recommended in many cultures as a means of stimulating milk secretion. On the other hand, excessive alcohol intake has been associated with failure to initiate the let-down reflex (see Chapter 5), high alcohol levels in the milk, and lethargic nurslings (Cobo, 1973), as well as with adverse health consequences for the mother. Wilson and colleagues (1980) comment: ''The observation that acetaldehyde, the major metabolite of ethanol, is not excreted in the milk is significant since some have postulated that acetaldehyde contributes to the toxicity of alcohol" (p. 34). In a study of 1-year-old infants, Little and colleagues (1989) found a strong positive association between psychomotor development scores obtained with the Bayley Scales of Infant Development (Bayley, 1969) and a proxy measure for exposure to alcohol