VOL 53: JANUARY • JANVIER 2007 Canadian Family Physician • Le Médecin de famille canadien 33 Motherisk Update C odeine is commonly used in the postpartum period for pain associated with episiotomy and cesar- ian section. As most mothers initiate breastfeeding, the safety of codeine and its pharmacologically active metabolite, morphine, among breastfed infants is of pri- mary concern. The American Academy of Pediatrics and major authoritative texts list codeine as compatible with breastfeeding, 1,2 despite insufficient published data to support this recommendation. To illustrate the need for further assessment of codeine and morphine transfer into breast milk, we describe a recently published case of a full-term, breastfed infant who died in a manner consistent with morphine overdose. 3 Pharmacogenetic assessment of maternal drug biotransformation was consistent with enhanced formation of the pharma- cologically active opioid, morphine. To the best of our knowledge, this is the first record of a breastfed baby succumbing to toxicity through breast milk. Case A newborn male infant, born after an unremarkable pregnancy and delivery (birth weight 3.88 kg, 90th percentile), developed difficulty breastfeeding and increasing lethargy at 7 days of age. At 11 days of age, he was taken to a pediatrician owing to concerns about his skin colour and decreased milk intake. The pediatrician noted that the infant had gained his birth weight. Subsequently, on day 13, an ambulance team found the baby cyanotic and without vital signs. Resuscitation, which was initiated at home and con- tinued in the hospital’s emergency department, was unsuccessful. Full postmortem analysis failed to iden- tify an anatomic cause of death. Hepatic steatosis was investigated for medium- chain acyl-CoA dehydrogenase deficiency, which was ruled out. Other fatty acid oxidative disorders, organic acidemias, congenital adrenal hyperpla- sia, hypothyroidism, and galactosemia were also ruled out. Postmortem toxicologic testing using gas chromatography–mass spectrometry revealed a blood concentration of morphine at 70 ng/mL and acet- aminophen at 5.9 μg/mL. Neonates receiving mor- phine for analgesia have been reported to have serum concentrations of morphine at 10 to 12 ng/mL. 4 Review of the medical records revealed that in the immediate postpartum period the mother was Safety of codeine during breastfeeding Fatal morphine poisoning in the breastfed neonate of a mother prescribed codeine Parvaz Madadi Gideon Koren, MD, FRCPC James Cairns, MD David Chitayat, MD Andrea Gaedigk, PHD J. Steven Leeder, PHARMD, PHD Ronni Teitelbaum, MSC Tatyana Karaskov, MD Katarina Aleksa, PHD FOR PRESCRIBING INFORMATION SEE PAGE 143  Current Practice • Pratique courante ABSTRACT QUESTION Recently a newborn died from morphine poisoning when his mother used codeine while breastfeeding. Many patients receive codeine for postlabour pain. Is it safe to prescribe codeine for nursing mothers? ANSWER When a mother is an ultrarapid metabolizer of cytochrome P450 2D6, she produces much more morphine when taking codeine than most people do. In this situation, newborns might be exposed to toxic levels of morphine when breastfeeding. Options to reduce this risk include discontinuing codeine after 2 to 3 days of use and being aware of symptoms of potential opioid toxicity in both mothers and newborns. RÉSUMÉ QUESTION Un nouveau-né est récemment décédé d’un empoisonnement à la morphine parce que sa mère avait pris de la codéine pendant qu’elle allaitait. De nombreuses patientes reçoivent de la codéine pour les douleurs après le travail. Est-il sécuritaire de prescrire de la codéine aux mères qui allaitent? RÉPONSE Si la mère métabolise ultra rapidement le cytochrome P450 2D6, elle produit beaucoup plus de morphine lorsqu’elle prend de la codéine que la plupart des autres personnes. Dans une telle situation, un nouveau-né pourrait être exposé à des taux toxiques de morphine quand il est allaité. Pour réduire le risque, on peut, entre autres, cesser l’utilisation de la codéine après 2 ou 3 jours, et demeurer vigilant face aux éventuels symptômes d’une intoxication aux opioïdes chez la mère et le nourrisson.