Boxed warning

In USA drugs that have special problems, particularly ones that may lead to death or serious injury, may have this warning information displayed within a box in the prescribing information. This is often referred to as a “boxed” or “black box” warning. Drugs that have such boxed warnings are not permitted to have reminder ads.
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.