Black box warnings may not deter physicians' prescribing

Seven out of 1,000 outpatients received a prescription violating a black box warning, according to a study in the Archives of Internal Medicine (2/13/2006). Although few adverse drug events resulted among these patients (<1%), the researchers estimate that one in six patients who were prescribed a drug despite a black box warning had the potential for an adverse event.

The study's researchers analyzed the electronic medical records of 324,548 outpatients who received at least one prescription in an ambulatory practice in the greater Boston area in 2002. Of the 33,778 prescriptions, over 2,300 were written in violation of a black box warning. Nearly 91% of patients received a prescription for a condition for which the drug was not recommended. Some patients also received a prescription with a black box warning for drug-laboratory interaction (26.6%) and drug-drug interaction (3.3%). Moreover, patients who were 75 years of age or older, white, and female and who took more medications were more likely to receive a drug in violation of a black box warning than younger, male, nonwhite patients taking fewer medications.

The researchers acknowledge that black box warnings are often vague and difficult to understand. They may also be inconsistent with clinical practice guidelines. To increase adherence to these warnings, the researchers are calling on the Food and Drug Administration to make them more specific, readily understandable to prescribing providers, and consistent with commonly used practice guidelines.