Codeine Use by Nursing Mothers Could Endanger Infants

Concern about a rare but potentially serious side effect in nursing infants whose mothers are taking codeine recently led the FDA to issue a public health advisory on the use of medications that include the ingredient. Nursing mothers who are ultra-rapid metabolizers of codeine run the risk of passing potentially lethal amounts of the drug on to their infants.

Some people, because of their genetic makeup, metabolize codeine faster and more completely than others. These "ultra-rapid metabolizers" are likely to have high levels of morphine in their blood after taking a medication that includes codeine. Nursing mothers who are ultra-rapid metabolizers may have higher-than-expected levels of morphine in their breast milk.

Although the number of reported cases of infants who have experienced morphine overdose via this route is small, the potential effects are serious, says an FDA press release. Signs of morphine overdose in such infants include increased sleepiness, difficulty breastfeeding, breathing difficulties or limpness. Nursing mothers also may experience overdose symptoms such as extreme sleepiness, confusion, shallow breathing or severe constipation.

Although one FDA-approved genetic test for determining whether a given individual has an ultra-rapid metabolism exists, its sensitivity for codeine metabolism is limited.

According to an FDA alert aimed at health care professionals, physicians who prescribe medications containing codeine to nursing mothers should prescribe the lowest effective dose for the shortest time possible. If a nursing mother is known or suspected to be an ultra-rapid metabolizer of codeine, physicians are encouraged to consider other possibilities when prescribing a medication for pain or cough. If a medication that contains codeine must be used, physicians should monitor the mother and her infant closely.

The FDA also recommends informing the infant's physician about the mother's use of codeine. In addition, physicians should tell nursing mothers that when their pain or cough improves, they should switch to a medication that does not contain codeine.

For many years, codeine has been considered among the safest narcotic pain relievers for nursing mothers and their infants. However, to raise awareness of the possible adverse effects of codeine on breastfeeding infants, the FDA is requiring manufacturers of prescription drugs that include codeine to include information about codeine ultra-rapid metabolism in their drug package insert information. The FDA also has included information on its Web site about this topic, both for consumers and for health care professionals.

Physicians caring for infants who exhibit symptoms of morphine overdose that may be tied to codeine ultra-rapid metabolism should alert MedWatch, the FDA's Safety Information and Adverse Event Reporting Program.