Very small amounts of codeine can be excreted in human breast mil which can pose a risk to a nursing infant. The Food & Drug Administration issued a Public Health Advisory pertaining to a severe (but very rare) side effect that can occur in nursing infants whose mothers take codeine. Because codeine is metabolized as morphine, and because some people metabolize the drug much more rapidly than others, there is a risk that some infants (those who are ultra-rapid metabolizers of codeine) can suffer from apnea, bradycardia, and cyanosis during their first week of life if their mother is nursing and taking codeine.
The potential risk for hazardous problems to occur when using codeine while nursing is actually rather small which is why the American Academy of Pediatrics considers codeine compatible with breast-feeding. In most cases, though very small traces of codeine can be passed down to the baby through breast-feeding, the effects are not highly dangerous to the baby. The primary risk is in the rate at which a person metabolizes the codeine into morphine. For ultra-rapid metabolizers, there is severe risk but this is not typically known until the drug is already in the system.
Doctors who prescribe codeine containing drugs to nursing mothers are encouraged to recommend the lowest possible dose and for the shortest possible period of time to ensure the safest use of the drug by these patients. Patients should also be very closely monitored to ensure the safety of both the mother and the nursing infant while codeine is being used.
There is a test that has been cleared by the FDA to determine a patient’s CYP450 2D6 genotype which has been connected with ultra-rapid metabolization of codeine. Though the test is not routinely used in clinical practice, it can be used in labs to determine a patient’s risk of ultra-rapid metabolization of codeine and to subsequently make better decisions regarding the prescribing of such a medication to a nursing mother. Some are at a higher risk than others and this too can be addressed by doctors prior to prescribing the medication.