Codeine and Breastfeeding: Safety Considerations

Risk Assessment

Codeine is a prodrug metabolized to morphine by the CYP2D6 enzyme system, with significant genetic variability in metabolism rates across populations 3, 4
Women who are ultrarapid metabolizers (up to 28% in Middle Eastern/North African populations, up to 10% in Caucasians) produce much higher concentrations of morphine in breast milk 3, 4
This variability creates unpredictable infant exposure, with documented cases of severe neonatal depression and death 3, 2
Codeine is secreted in breast milk due to high lipophilicity and weak protein binding, with potential for metabolism by the infant 1, 2

The US Food and Drug Administration (FDA) and European Medicines Agency advise against codeine use in breastfeeding women 1, 3
The Association of Anaesthetists recommends against codeine use given the availability of safer alternatives 1, 3

Dihydrocodeine may be preferred if a weak opioid is needed, due to its cleaner metabolism compared to codeine 1, 6
Morphine is recommended as the opioid of choice if strong analgesia is required 5
If codeine has been taken by a breastfeeding woman, discard breast milk for 15 hours to allow full clearance from maternal plasma 1, 6
Monitor the infant for signs of opioid toxicity including increased sleepiness, difficulty breastfeeding, respiratory depression, and decreased alertness 1, 3

Genetic testing for CYP2D6 ultrarapid metabolizer status is not routinely available, making it impossible to predict which mother-infant pairs may experience severe adverse effects 3, 4
The proportion of ultrarapid metabolizers varies significantly by ethnicity (1% in Asians to 28% in Middle Eastern/North African populations), creating variable risk profiles 3, 4

Failing to recognize that even moderate codeine doses that appear safe in most women can cause severe toxicity in infants of ultrarapid metabolizers 3, 4
Not considering the risks of codeine use during breastfeeding, as safer alternatives exist 1