Study Reveals Inconsistencies in Black Box Warnings

Researchers uncovered differences in medication labels that threaten to compromise drug safety.

A new study shows that black box warnings—often the last line of defense against serious adverse events—are inconsistent among prescription drugs of the same class. The differences could leave patients largely unaware of potential risks of the medications they are taking, researchers said.

In a report published in the February issue of the Journal of General Internal Medicine, investigators from the University of Ionnanina School of Medicine in Greece and Stanford University School of Medicine wrote that black box labeling “requires transparent and systematic rules, as well as clear justification for the presence of, or lack of evidence for, specific major risks for individual drugs.”

Currently, drugs are assigned black box warnings according to their pharmacologic class, since adverse events tend to apply to entire classes of drugs. For their study, the researchers looked at whether some drugs lacked the same black box warning as others of the same class, as well as the amount of time it takes to add necessary warnings to drugs in the same class.

They selected a total of 176 drugs from 20 of the top-selling drug categories of 2008. Of the 20 categories, 10 carried a black box warning. Among the 176 drugs studied, 7 were withdrawn due to safety concerns. These concerns were rarely mentioned in black box warnings for drugs that remained in that category, the authors noted.

They observed additional differences in 9 of the 20 categories, with a total of 15 black box warnings applied inconsistently to drugs within the same class. Information from 10 of the 15 black warnings appeared on the label as “simple warnings or text,” and the same information was completely absent in 5 of the black box warnings.

In addition, there was “a considerable time-lag in black box warning acquisition” for the 10 drug classes with 1 or more black box warnings, according to a news release on the study. The interval ranged from as short as 2 months to as long as 14 years for some drugs.

The researchers said labeling needs to “become more systematic” to ensure patients are aware of the risks of a given class of drugs. “Absence of a [black box warning] or asynchronous addition of a [black box warning] among same-class drugs could have major implications,” they concluded.

For other articles in this issue, see:

• Flu Spreads Faster Through Same-Gender Friendships
• Spike in Pharmacy Robberies Prompts NYT Exposé