Because many pediatric doses are calculated—eg, using body weight—rather than simply read from a list, major dosing errors may result from incorrect calculations. Typically, tenfold errors due to incorrect placement of the decimal point have been described. In the case of digoxin, for example, an intended dose of 0.1 mL containing 5 mcg of drug, when replaced by 1.0 mL— which is still a small volume—can result in a fatal overdose. Different strategies have been developed to prevent these potentially fatal errors. For drugs with narrow therapeutic windows (eg, digoxin, insulin, potassium), independent double-checking of dose and volume calculations is widely practiced. A good rule for avoiding such “decimal point” errors is to use a leading “0” plus decimal point when dealing with doses less than “1” and to avoid using a zero after a decimal point (see Chapter 65).
remember that, compared with breast-feeding, formula feeding is associated with higher infant morbidity and mortality in all Despite the fact that most drugs are excreted into breast milk in socioeconomic groups. amounts too small to adversely affect neonatal health, thousands Most drugs administered to lactating women are detectable in of women taking medications do not breast-feed because of breast milk. Fortunately, the concentration of drugs achieved in fears of harming the baby and misperception of risk. Unfortu-breast milk is usually low (Table 59–5). Therefore, the total amount nately, physicians often contribute to this bias. It is important to the infant would receive in a day is substantially less than what
TABLE 59–5 Drugs often used during lactation and possible effects on the nursing infant.
would be considered a “therapeutic dose.” If the nursing mother must take medications and the drug is a relatively safe one, she should optimally take it 30–60 minutes after nursing and 3–4 hours before the next feeding. In some cases this may allow time for drugs to be partially cleared from the mother’s blood, and the concentrations in breast milk will be relatively low. Most antibiotics taken by nursing mothers can be detected in breast milk. Tetracycline concentrations in breast milk are approximately 70% of maternal serum concentrations and present a risk of permanent tooth staining in the infant. Isoniazid rapidly reaches equilibrium between breast milk and maternal blood. The concentrations achieved in breast milk are high enough so that signs of pyridoxine deficiency may occur in the infant if the mother is not given pyridoxine supplements.
Most sedatives and hypnotics achieve concentrations in breast milk sufficient to produce a pharmacologic effect in some infants. Barbiturates taken in hypnotic doses by the mother can produce lethargy, sedation, and poor suck reflexes in the infant. Chloral hydrate can produce sedation if the infant is fed at peak milk concentrations. Diazepam can have a sedative effect on the nursing infant, but, most importantly, its long half-life can result in significant drug accumulation.