Black box warning

In the United States, a boxed warning (sometimes "black box warning", colloquially) is a warning that death or serious injury may result from the use of a particular drug. It appears near the beginning of the package insert for certain prescription drugs and biologics, so called because the U.S. Food and Drug Administration specifies that it be concise and be formatted with a "box" or border around the text and a heading in all caps, containing "WARNING", to emphasize its importance. The FDA can require a pharmaceutical company to place a boxed warning. It is the strongest warning that the FDA requires, and signifies that medical studies indicate that the drug carries a significant risk of preventable, serious or even life-threatening adverse effects.

Economists and physicians have thoroughly studied the effects of FDA black box warnings on prescription patterns. It is not necessarily true that a physician and patient will have a conversation about a drug's black box warning after it is issued. For instance, an FDA-mandated boxed warning decreased rosiglitazone (Avandia) use by 70%, but that still meant 3.8 million people were given the drug. Later research indicated that after receiving an FDA advisory, there was a decrease in rosiglitazone use, due to a combined effect of media exposure, advisory, and scientific publications, whereas pioglitazone (with a similar advisory and black box warning but less media exposure) did not similarly decrease in use; it increased.