In the United States, a boxed warning (sometimes "black box warning", colloquially) is a type of warning that appears near the beginning of the package insert for certain prescription drugs, so called because the U.S. Food and Drug Administration specifies that it is formatted with a 'box' or border around the text to emphasize it is of utmost 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 boxed warnings on prescription patterns. It is not necessarily true that a physician and patient will have a conversation about a drug's boxed warning after it is issued. For instance, an FDA-mandated boxed warning decreased rosiglitazone 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 but less media exposure) did not similarly decrease in use.

Examples

Boxed warnings on drugs have received increased media attention in the United States since 2004. Among some of the more widely covered stories:

In other jurisdictions

In China, a warning text (警示语) may be added to a package insert, either voluntarily by the manufacturer or at the request of NMPA (formerly CFDA, the Chinese counterpart of FDA). Although no formatting requirement is found in law, the typical formatting is similar to the American counterpart with boxed text at the top of the insert. The CFDA/NMPA has used its power to mandate a warning on fluoroquinolones, ceftriaxone, aciclovir, and pioglitazone. Health Canada terms its version of boxed warnings "serious warnings and precautions box". The formatting is similar to the US counterpart; an example for Paxlovid can be seen on Pfizer's website.