The Food and Drug Administration (FDA) has issued a warning about the use of codeine by nursing mothers after the publication of a case report of a breastfed infant who died after its mother had received the drug to alleviate pain from an episiotomy. The death appears to have been due to a genetic variation in the mother that caused her to metabolize codeine more rapidly than normal. Most drugs become inactive once they are metabolized, but codeine is converted into active morphine, and patients who metabolize codeine very rapidly and more completely are likely to have levels of circulating morphine that are higher than normal. A genetic test can determine whether a patient is a rapid metabolizer, but how to interpret the results is not yet understood well enough to be able to predict whether metabolized codeine-morphine-will be passed into breast milk. Therefore, nurses should advise women who are taking codeine or codeine-containing products that some of the narcotic passes into breast milk and therefore to the nursing infant. Mothers should be instructed to minimize the dose of codeine and the duration of its use and to monitor infants for possible signs of overdosage--their infant is sleeping more than four hours consecutively, isn't breastfeeding every two to three hours, has difficulty breathing, and is limp. If any of those signs is present, the nursing mother should stop taking codeine and contact her physician, pediatrician, or both.