The article "Using Medications in Pregnancy and Lactation" (MCN 30[1], January 2005) is a very good integration of the physiology of pregnancy and lactation and the use of medications.

I do have one question: there is a statement that "Only unbound drugs are capable of crossing the placenta; because of this, protein-bound drugs (such as digoxin or ampicillin) can reach higher concentrations in the fetus (Loebstein et al., 1997)." I don't understand this; if digoxin or ampicillin are protein-bound, they should not be able to cross the placenta to create higher concentrations in the fetus. Could you please clarify this for me?

Shannon Perry, PhD, RN, FAAN