In the
United States, a
boxed warning (sometimes
'black box warning', colloquially) is a type of warning that appears on 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. The FDA can require a
pharmaceutical company to place a boxed warning on the labeling of a prescription drug, or in literature describing it. It is the strongest warning that the FDA requires, and signifies that medical studies indicate that the drug carries a significant risk of serious or even life-threatening
adverse effects.