Beyond the federal rules, guidelines by doctors' groups give physicians wide latitude to talk about off-label use.
Such off-label use of approved medications is legal and commonplace in American medicine.
The pharmaceutical company isn't allowed to give you medicine for an off-label use.
It has been estimated that more than half of all prescriptions written nationwide are for off-label uses.
Actimmune's sales represent an extreme case of what is known as off-label use.
Drug companies may not promote or market drugs for off-label uses.
"The insurance company will decline to pay, because that is considered experimental or off-label use of drugs."
But experts say such "off-label" use of the drugs can be risky.
However, there is often extensive medical literature to support the off-label use.
In general, such methods may hold important opportunities for off-label use of existing approved drugs.