Based on minimal excretion of other phenothiazine derivatives, it appears that occasional short-term use of promethazine for the treatment of nausea and vomiting poses little risk to the breastfed infant. With repeated doses, observe infants for excess sedation. Because promethazine can lower basal prolactin secretion, promethazine might interfere with the establishment of lactation if given during labor before lactation is well established or with a sympathomimetic such as pseudoephedrine. An antiemetic without potent histamine blocking action is preferred in nursing mothers.