N02AA01

It is an opioid agonist used for the relief of moderate to severe acute and chronic pain. It is the main alkaloid of opium, which is obtained from whole opium poppies (Papaver somniferum). Oral, epidural, subcutaneous, intramuscular, or intravenous administration

It is excreted in breast milk in moderate amounts ^{(Baka 2002, Robieux 1990, Wittels 1990, Feilberg 1989)}, which could be clinically significant (RID ≥ 9%). When administered epidurally, excretion in milk is negligible. ^{(Oberlander 2000, Zakowski 1993, Feilberg 1989)}

In addition, a low oral bioavailability makes that the amount present in the infant's plasma due to absorption from milk by the gut is low. ^{(Reece 2017, Worthington 2013)}

Low to moderate levels of drug has been found in the plasma of infants from treated mothers ^{(Robieux 1990, Naumburg 1987)} and harmful effects in the infants were not reported. ^{(Zipursky 2023, Patricelli 2022,  Worthington 2013, Hendrickson 2012, Robieux 1990)}

There are fewer breastfeeding dropouts, lower milk levels, and fewer side effects in infants of mothers treated with morphine than with pethidine. ^{(Yost 2004, Wittels 1997)}

Analgesia used during the birth process is related to a brief delayed of stage II of Lactogenesis (milk come-in) ^{(Lind 2014)}. No difference in breastfeeding rates at 6 weeks has been found in mothers who received subcutaneous morphine, epidural fentanyl, or nothing during labor and delivery ^{(Mahomed 2019)}. No differences were found in the frequency of breastfeeding in the first hour in mothers who received epidural morphine or fentanyl or no epidural analgesia during labor and delivery ^{(Fan 2020)}. Ketorolac, ibuprofen, and paracetamol for post-cesarean section analgesia improve breastfeeding initiation rates compared to morphine analgesia. ^{(Macias 2022)}

Morphine can increase Prolactin levels ^{(Moshtaghi 2005, Zis 1984, Tolis 1975)} and may decrease Oxytocin levels ^(Lindow1999), but it would not be determinant for already established lactations.

Avoidance of repetitive or chronic use and follow-up for somnolence and adequacy of infant nourishment is recommended ^{(WHO 2002)}. Bed-sharing with the baby is not recommended if drugs are used due to increased risk of suffocation or sudden infant death. (ABM 2020 &2008, UNICEF 2019, 2017, 2014 & 2013, Landa 2012, UNICEF 2006)

Some authorities consider Morphine as the elective opioid medication for breastfeeding mothers ^{(Lamvu 2018, Reece 2017, Worthington 2013, Rowe 2013, Sachs 2013, Howie 2006, Bar-Oz 2003, Spigset 2000, Ravin 1995)}. Recommendations for Drugs in the Eleventh WHO Model List of Essential Drugs: compatible with Breastfeeding in occasional doses. ^{(WHO 2002)}. American Academy of Pediatrics: medication usually compatible with breastfeeding.^{(AAP 2001)}