All medications are secreted into the breast milk, although concentrations appear to vary. There is a fair amount of information on the use of Paxil (paroxetine) in nursing women. While Paxil may be detected in the breast milk, there have been no reports of adverse events in the nursing infant. The only situation where one may want to avoid breastfeeding is when the baby is premature or has signs of hepatic immaturity, which may make it more difficult for the infant to metabolize the medication to which he or she is exposed. Premature babies are also probably more vulnerable to the toxic effects of these medications.
There may be some ways to minimize the amount of medication to which the nursing infant is exposed. First, the lowest dose of medication that is effective should be used. Second, in older infants, it may be possible to time the feedings so as to minimize exposure. The levels of Paxil in the breast milk peak about 8 hours after ingestion of medication and decline thereafter, reaching the lowest levels immediately before the next dose of medication is to be taken. Theoretically, the amount of medication to which the infant is exposed could be reduced by avoiding nursing during times at which the medication concentration in the breast milk would be the highest (i.e., 8 hours after taking the medication). Studies with sertraline (Zoloft) indicate that this approach leads to a 20% reduction in the amount of medication to which the infant is exposed. While this strategy may be attractive, it may prove to be more cumbersome in a newborn who is nursing on demand.
Ruta Nonacs, MD PhD