Off-label use is the use of pharmaceutical drugs for an unapproved indication or in an unapproved age group, unapproved dosage, or unapproved form of administration. Both prescription drugs and over-the-counter drugs(OTCs) can be used in off-label ways, although most study of off-label use centers on prescription drugs. Off-label use is generally legal unless it violates specific ethical guidelines or safety regulations.
In the United States, no law prohibits a physician or other healthcare practitioner from prescribing an approved medication for other uses than their specific FDA-approved indications.
However, once a drug has been approved for sale for one purpose, physicians are free to prescribe it for any other purpose that in their professional judgment is both safe and effective, and are not limited to official, FDA-approved indications. This off-label prescribing is most commonly done with older, generic medications that have found new uses but have not had the formal (and often costly) applications and studies required by the FDA to formally approve the drug for these new indications. However, there is often extensive medical literature to support the off-label use.
The FDA does not have the legal authority to regulate the practice of the medicine, and the physician may prescribe a drug off-label.