Black Box Warnings Under Scrutiny
The so-called "black box" warnings that appear on prescription drug labels may contain language so unclear that doctors cannot interpret their meaning, according to researchers in Boston.
Researchers Karen E Lasser, MD, MPH, of the Cambridge Health Alliance, and colleagues have called on the US Food and Drug Administration (FDA) to improve the language in these warnings, so that doctors can interpret them more easily.
Their study was published in the Archives of Internal Medicine and reported by MedPage Today on February 14, 2006.
The authors estimate that 7% of patients who receive a drug with a black box warning also receive prescriptions that violate the warning. They believe that the warnings' poor wording is at fault, saying that some of the warnings require a specialist to interpret them.
"Our results suggest that-the absolute number of outpatients at risk is substantial," Dr Lasser and colleagues at Harvard Medical School wrote.
"We believe these data have implications for the Food and Drug Administration, the developer of black box warnings. The [FDA] should make these warnings more specific, so that they are readily understandable by providers, and so that such providers can easily take action to avoid violating the warnings."
Study Protocol
Dr Lasser and colleagues analyzed medical records of 324,548 patients from 51 outpatient practices in the greater Boston area who received a prescription medication in 2002. About 30,000 patients received a drug with a black box warning, and 7% of them also received a prescription that violated the warning.
According to the study, less than 1% of those who received a prescription that violated the warnings (i.e., 16 study patients) experienced an adverse drug event as a result.
The authors noted that the study may have underestimated the number of adverse drug events. They wrote, "our study was limited by the fact that we did not have access to visit or laboratory data outside of the HER [electronic health record]. Thus, we could not determine whether an ADE [adverse drug event] occurred in about a fifth of the records reviewed."
The violations were ascribed to poor wording of warnings: "In many cases, the warnings are vague and difficult to interpret. We found that more than half of the black box warnings required clarification from a specialist."
As examples of unclear wording, the researchers wrote: "The drug valproate sodium contains a black box warning to check liver function test results at frequent intervals, but does not specify how often to monitor such tests." They deemed terms such as "advanced renal impairment", "active liver disease", and "high dose" too vague to interpret.
"The Food and Drug Administration should make these warnings more specific, so that they are readily understandable by providers, and so that such providers can easily take action to avoid violating the warnings," the authors noted.
An FDA spokesperson said that the FDA had no comment, according to MedPage Today.
Physicians may fail to heed black box warnings also because some warnings conflict with standard guidelines, said the investigators. For example, American Psychiatric Association guidelines state that blood levels of lithium should be monitored every 3-6 months, but the drug's black box warning says that monitoring should occur at least every two months, according to MedPage Today.
"Remembering all these warnings is beyond the capability of the human mind," the authors wrote.
"If providers are to consider these warnings, it is essential that at least the most frequently violated warnings be compiled and made available through decision support in electronic health records."
Source: Black Box Warnings Called Too Vague for Compliance, MedPage Today, February 14, 2006. Adherence to black box warnings for prescription medications in outpatients. Lasser KE et al. Archives of Internal Medicine, volume 166, pages 338-334, February 2006.
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