ROBERT SIEGEL, host:
Today, the Food and Drug Administration issued an advisory to physicians and nursing mothers about the painkiller most widely used after childbirth.
NPR's Joanne Silberner reports that the agency still backs the use of codeine for new mothers, but says it should be used carefully.
JOANNE SILBERNER: Two years ago, a 13-day-old infant died in Canada. His mother had been prescribed codeine after an episiotomy. No one realized she was a supermetabolizer. Her body broke down codeine into its active form, morphine, too quickly. Morphine flooded into her breast milk. That's bad because too much morphine can cause drowsiness and interfere with breathing, says Sandra Kweder of the FDA.
Dr. SANDRA KWEDER (Deputy Director, Office of New Drugs, FDA): Infants who are exposed to very high levels of morphine through breast milk can experience those side effects very severely and in fact get an overdose of the drug.
SILBERNER: Kweder says that sort of overdose is rare. There's just the one reported death. Cough syrups and painkillers that contain codeine have been used for decades and no one's noticed other problems. Still it was enough to prompt the agency to issue a warning.
Dr. KWEDER: If you're a nursing mother taking codeine, call your doctor if you become extremely sleepy to the point where you're having difficulty taking care of your baby. It could be a sign that you're metabolizing the drug more rapidly than most people.
SILBERNER: Somewhere between 1 percent and 10 percent of people metabolize codeine rapidly. There's a genetic test, but it's expensive and not widely available. At this point, instead of testing all nursing moms, the FDA says doctors should simply prescribe the lowest dose of codeine for the shortest time and carefully watch for side effects in mother and child.
Alan Garber heads the Center for Health Policy at Stanford. He says this sort of genetic testing has promise, but is still not all that useful for most people.
Dr. ALAN GARBER (Director, Center for Health Research and Policy, Stanford University): That's something that's been in the future for many years and, for the most part, it's still in the future.
SILBERNER: Right now, it's easy enough to recognize nursing moms who metabolize codeine too quickly by their symptoms, or their babies' symptoms, without doing a genetic test. Still, FDA officials have hopes for such testing.
Janet Woodcock is the FDA's chief medical officer.
Dr. JANET WOODCOCK (Chief Medical Officer, FDA): This is a theme that we are trying to develop that looks at the scientific basis for why people respond differently, so that we can predict and then prevent safety problems in people that are based on these known causes.
SILBERNER: The agency has an initiative aimed at using genetics to figure out who is vulnerable to side effects before they ever take a drug.
Joanne Silberner, NPR News.