GETTYIMAGES, TOOGA
In 2005, a mother who had just given birth received codeine to dull the pain associated with childbirth. In her body, the codeine was converted into morphine by a drug-metabolizing enzyme called CYP2D6. Although people carry many variations in the gene for this enzyme, this woman had an unusual difference: she expressed multiple copies of the gene. As a result, the additional CYP2D6 enzymes in her body churned through the codeine so efficiently that her morphine levels spiked and stayed high. Unbeknownst to her doctors, high doses of the drug had passed from her milk into her infant. When the baby was brought back to the hospital with gray skin 12 days after his birth, doctors were puzzled. He was an otherwise healthy baby boy. ...
