 . . says the FDA, because nursing infants could suffer morphine overdose.  

Some humans, because of genetic predisposition, convert codeine to morphine faster and more completely. If an infant is an ultra-rapid metabolizer, he or she may overdose on the amount of codeine contained in mother's milk. Similarly, if the mother is an ultra-rapid metabolizer, her milk may contain higher than normal levels of morphine.  

Remind patients that codeine can be found in over-the-counter, as well as prescription medications, so they should check labels and take the lowest amount possible. Also advise nursing moms taking codeine or other narcotic pain relievers to watch for the following signs of overdose in their babies, including increased sleepiness, difficulty breastfeeding or breathing, and limpness.  

. . .says the FDA, because nurisng infants could suffer morphine overdose.