Published: December 2010
Links updated: October 2015

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Codeine and Breastfeeding

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Prescriber Update 31(4): 26
December 2010

Healthcare professionals are reminded that codeine use by breastfeeding mothers has been associated with fatal cases of infant morphine toxicity. Healthcare professionals should carefully consider the risks and benefits of codeine before recommending its use to breastfeeding mothers.

The labels for over-the-counter (OTC) products containing codeine have recently been updated to advise against codeine use in breastfeeding except on medical advice. The doses of codeine available in some OTC preparations are considered sufficient to cause morphine toxicity in breastfed infants.

The Lancet published a case report in 2006¹ of an otherwise healthy 13 day old breastfed baby who died of morphine toxicity after his mother had been prescribed codeine (60mg twice daily for 2 days and then 30mg twice daily thereafter) to treat episiotomy pain. The baby experienced feeding difficulties and lethargy at day 7 and was found dead on day 13. Analyses of the baby's blood and the mother's breast milk found toxic levels of morphine in both. Genetic testing of the mother determined that she was an ultra-rapid metaboliser (URM) of codeine, leading to an increase in the rate and extent of conversion of codeine to morphine.

The prevalence of URM of codeine varies among different racial groups.² It is estimated that 1-10% of Caucasians are URMs; although it is unknown what proportion of Maori or Pacific people are affected. In the absence of genetic testing, it is not possible to identify URMs prior to prescribing codeine.

Patients should be advised of the symptoms of morphine toxicity in themselves (nausea, vomiting, somnolence, constipation and/or difficulty caring for the baby) and their baby (increased sleepiness, difficulty breastfeeding, breathing difficulties or limpness). Patients should be advised to discontinue codeine and to seek medical attention immediately if these symptoms occur.

References

1. Koren G, et al (2006). Pharmacogenetics of morphine poisoning in a breastfed neonate of a codeine-prescribed mother. Lancet 368:704.
2. FDA Public Health Advisory: Use of codeine by some breastfeeding mothers may lead to life-threatening side effects in nursing babies. August 2007. http://www.fda.gov/NewsEvents/Newsroom/PressAnnouncements/2007/ucm108968.htm
3. PSM Healthcare Ltd t/a API Consumer Brands. 21 January 2013. Codeine Phosphate data sheet. www.medsafe.govt.nz/profs/Datasheet/c/CodeinePhosphatePSMtab.pdf