Judicious use of opioids in the perioperative setting is largely considered safe for breastfeeding mothers, however this is a class of medication with real potential for milk transfer and infant side effects. Opioids can be given by multiple different routes, but are generally used in intravenous and oral forms in the perioperative setting.
Medications usually given by the intravenous route include fentanyl, morphine, and hydromorphone. Fentanyl exhibits low milk transfer and extremely low oral bioavailability, and as such is likely the safest opioid to use perioperatively. Morphine and hydromorphone do have some oral availability, but at 3-5 times the dose needed when given by mouth instead of intravenous route. At typical doses used in the operating room and immediately post-operatively, these medications are considered safe if the mother plans to breastfeed. Caution is urged, however, if mothers require multiple high doses of these medications post-operatively. Other medications such as remifentanil, sufentanil, and nalbuphine may also be used during anesthesia, and their intra-operative use should not preclude breastfeeding once the mother is awake and alert.
Oral opioids include oxycodone, hydrocodone, codeine, and tramadol. The FDA issued a “black box warning” in 2017 against the use of codeine and tramadol in breastfeeding mothers, owing to interindividual variation in metabolism of these pro-drug medications that could result in a relative overdose of their respective active analgesic metabolites morphine and o-desmethyltramadol. Thus oxycodone and hydrocodone remain the primary options for short courses of oral opioids for acute pain. As with any opioid use for any pain issue, these should be given at the lowest effective dose and for the shortest necessary time. LactMed suggests a maximum dose of 30 mg/24 hours in divided doses for each of these medications; infants should be monitored and cared for by a responsible adult other than the mother if they are exposed to oral opioids through breastmilk. In the newborn, the dose the infant receives increases greatly when the mother’s milk comes in (lactogenesis II) because of the increased milk volume, so caution is advised.
Morphine and hydromorphone may also be given via the oral route instead of hydrocodone or oxycodone. These medications have poorer oral availability than oxycodone and hydrocodone, but may still result in clinically significant infant exposure. Further study is needed on whether these medications may represent a slightly safer alternative to oxycodone and hydrocodone. In general, opioids should be considered as adjuncts to a baseline analgesia of nonopioids, such as acetaminophen or ibuprofen, rather than first-line analgesics.