This week on The Tox Lab, we’re examining the controversial 2006 Lancet paper on codeine and fatal opioid toxicity in a breastfed infant.

We begin by introducing the paper and the case at its centre, in which an infant developed fatal opioid toxicity following exposure to codeine via breast milk.

We then explore the proposed mechanism, focusing on the role of CYP2D6 metabolism and how variability in this pathway may lead to higher-than-expected morphine concentrations.

We also discuss the limitations and criticisms of the paper, including questions around causality, alternative explanations, and the extent to which pharmacogenetics alone can account for the outcome.

Finally, we consider the wider impact of this publication, including changes to clinical guidance, prescribing practices, and the ongoing debate around codeine use in breastfeeding individuals.

Join us as we examine the pharmacology, pharmacogenetics, and controversy surrounding this landmark case, and consider what this means for clinical toxicology and patient safety.

Hope you enjoy!

Links to the papers we discussed:

https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(06)69255-6/abstract

https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(26)00245-X/fulltext

https://www.thelancet.com/journals/lancet/article/PIIS0140673608612544/abstract https://ascpt.onlinelibrary.wiley.com/doi/10.1002/cpt.1882

Link to the New Yorker Article : https://www.newyorker.com/magazine/2026/02/02/did-a-celebrated-researcher-obscure-a-fatal-poisoning

Disclaimer: All opinions are our own.

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