Diane: One question I always ask when a medication is being used which is not compatible or for which there are no data, is: Is this the only medication which will work for this problem? Unless the mother has had sputum or blood cultures which show a bug that would only respond to clarithromycin (extremely doubtful!), there are several antibiotics which are excellent for pneumonia and are breastfeeding compatible. Some physicians just get comfortable prescribing a certain drug, even if it's not necessarily the only effective one available. Good luck, Alicia. [log in to unmask]