Nearly one-quarter of babies whose mothers took codeine while breastfeeding showed signs of central nervous system depression, according to a new study, suggesting the drug can transform mother's milk into a troubling brew.
Specifically, 17 of 72 babies became sedated or experienced abnormal breathing, including one who narrowly avoided a tragic reaction, according to Hospital for Sick Children researchers in collaboration with the University of Western Ontario.
“You cannot continue to give it [codeine] like candies,” Gideon Koren, lead author of the study published in the journal Clinical Pharmacology & Therapeutics, said in a telephone interview. “… In some cases, this can be life-threatening.”
Codeine is extremely prevalent: Dr. Koren estimated as many as 120,000 Canadian women a year receive the drug after childbirth. And although it has been known that some mothers carry multiple copies of a gene capable of converting the common pain reliever into strong concentrations of morphine, he said the study suggests the pharmacological phenomenon is broader than initially thought.
“Young babies are much more sensitive to narcotics than adults, even if you calculate per dose,” said Dr. Koren, who holds the Ivey Chair in Molecular Toxicology at the University of Western Ontario in London.
“… Not all of it may be life-threatening, but any CNS [central nervous system] depression is bad news, especially if kids have other reasons for SIDS [sudden infant death syndrome] or not remembering to breathe. This was a very important finding.”
Since patients were self-selected – the sample comprised women who called the Motherisk program at Sick Kids in Toronto for advice on the pain reliever from January of 2004 to January of 2007 – further study is required, said Dr. Koren, the program's director.
Although codeine is recommended by the American Academy of Pediatrics as being compatible with breastfeeding, Dr. Koren said that as a treatment for a mother's pain it cannot be considered safe for all breastfed infants.
Canadian pharmacies dispensed more than 5.3 million prescriptions for the codeine-and-acetaminophen combination pills last year, according to Madeline Gareau Lagden of IMS Health, a private health-information and consulting-services company that serves the pharmaceutical and health-care industries. The pills are made by several drug companies, the most popular product being Tylenol 3.
Strategies to prevent overdoses include taking minimal doses, not using the drug for more than four days, closely monitoring the baby for grogginess and, in suspected cases, providing the antidote naloxone. When a mother feels groggy, often the baby does as well. There are other pain-relieving drugs without codeine that nursing mothers can take. Testing women for the gene is considered less feasible, largely because of cost.
The chance of being an ultra-rapid metabolizer or holding multiple copies of the gene varies among population groups, from fewer than 1 per cent of Caucasians to about 30 per cent of Ethiopians.
Baby's death probed
It was the Ontario coroner's office and Dr. Koren's toxicology detective work more than two years ago that discovered the unexplained death of an apparently healthy 12-day-old boy, Tariq Jamieson, was because of a morphine overdose through breast milk.
The boy's mother, Rani Jamieson, an accountant, was instructed to take two tablets, each containing a mixture of 30 milligrams of codeine and 500 mg of acetaminophen, four times a day or every six hours to deal with episiotomy pain after his birth on April 18, 2005. On the second day, she cut the dose in half, taking one tablet every six hours.
“This drug was killing him,” Ms. Jamieson, now 36, said in an interview. “And we didn't know it.”
