A new study in JAMA reports that a significant reduction in the rate of dispensing of codeine to postpartum women was observed following public health advisories from the U.S. Food and Drug Administration (FDA) and Health Canada on potentially life-threatening adverse effects in infants of breastfeeding mothers taking codeine.

Because some patients are ultra-rapid metabolizers of codeine (prevalence ranging from 2–40%), nursing mothers carrying the gene variants for elevated activity of an enzyme that metabolizes codeine to morphine may produce breast milk with high levels of morphine that could lead to infant death from a drug-induced respiratory infection. The FDA issued a public health advisory on the potentially life-threatening adverse effects in infants of breastfeeding mothers taking codeine in August 2007, with Health Canada publishing a similar advisory in October 2008.

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Kate Smolina, PhD, of the University of British Columbia, Vancouver, Canada, and colleagues reviewed data on the rate of codeine dispensations before and after the two regulatory advisories among all women with live births between January 2002 and December 2011 in British Columbia. Of the 320,351 live births to 225,532 women, new mothers filled at least one codeine prescription during 47,095 postpartum periods. Prior to the FDA advisory, the monthly average for the proportion of postpartum mothers filling at least one codeine prescription was 17%. This declined to a monthly average of 9% from September to December 2011 at a 45% relative reduction over four years.

The authors add that the reduction could also reflect changes in patient and clinician behaviors, but that the speed and impact of the response suggests regulatory warnings can have a strong influence on dispensing habits.

For more information visit JAMANetwork.com.