Medications and Lactation: What PNPs Need to Know

Jennifer M. Marks, BS; Diane L. Spatz, PhD, RNC


J Pediatr Health Care. 2003;17(6) 

In This Article

Drug Half-Life

Half-life is the time necessary for the drug serum concentration to decrease by one-half and is affected by the drug's volume of distribution (Vd) and clearance. The longer the half-life (T1/2) of a drug, the greater the risk of its accumulation in the mother and in infant. Half-life varies considerably from one drug to another. For example, the half-life of lansoprazole is less than 2 hours, whereas that of digitoxin is approximately one week (Hale, 2002). When prescribing medications to breastfeeding mothers, short half-life drugs are preferred since they generally peak (PK or Cmax) rapidly and then are eliminated from the maternal plasma, thus exposing breast milk, and the infant, to reduced levels of the medication (Hale, 2002). Half-life can be used to determine whether the mother can successfully breastfeed by taking the medication immediately after nursing or before the infant's longest sleep period (Nice, Snyder, & Kotansky, 2000). If the half-life is short enough (i.e., 1 to 3 hours), then the drug level will have declined at the time the infant feeds (Hale, 2002). This may minimize drug transfer through breast milkby avoiding peak plasma and milk drug concentrations (Nice, et al., 2000). Long-acting or sustained release medications should be avoided whenever possible, as their long half-life (i.e., 12 to 24 hours) potentially exposes the infant to a medication at higher concentrations and for longer periods of time (Auerbach, 1999; Hale, 2002).

Medications with extremely long half-lives (i.e., greater than 12 hours) in pediatric patients may build up in the infant's plasma over time (Hale, 2002). Examples where higher drug concentrations in the infant can and periodically do occur are barbiturates, benzodiazepines, meperidine, and fluoxetine (Hale, 2002).

If the drug in question can be given directly to infants, then it is highly unlikely that the amount available to the infant through breast milk will exceed the appropriate routinely prescribed therapeutic pediatric dose (Auerbach, 1999). Such drugs can be considered safe for use by the lactating mother for her breastfeeding child (Auerbach, 1999). For example, common antibiotics are routinely prescribed for breastfeeding women with mastitis and few adverse effects have been described in their breastfeeding infants (Auerbach, 1999).


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