Breastfeeding with a little drug in the milk is almost always safer. In other words, being careful means continuing breastfeeding, not stopping. Remember that stopping breastfeeding for a week may result in permanent weaning since the baby may then not take the breast again. On the other hand, it should be taken into consideration that some babies may refuse to take the bottle completely, so that the advice to stop is not only wrong, but often impractical as well. On top of that it is easy to advise the mother to pump her milk while the baby is not breastfeeding, but this is not always easy in practice and the mother may end up painfully engorged.
Most drugs appear in the milk, but usually only in tiny amounts.
Although a very few drugs may still cause problems for infants even in tiny doses, this is not the case for the vast majority. In this day and age, it is rarely a problem to find a safe alternative. If the prescribing physician is not flexible, the mother should seek another opinion, but not stop breastfeeding. Furthermore, not all the drug in the mother's blood can get into the milk. Only the drug that is not attached to protein in the mother's blood can get into the milk.