Once a new prescription drug has been approved by the FDA, and prescriptions have been written and used by patients, patients and professionals may discover that there are additional symptoms or conditions the drug may treat effectively that were not among the reasons the drug was originally approved.
Knowing about these different ways the drug may be effective, a doctor may decide to prescribe the drug for one of these alternative reasons. Such a prescription is considered to be "off-label." The drug does not need to go through the FDA process for the off-label prescription.
In particular, generic drugs that have been in use for many years may be discovered to have alternative uses.
In the US, it is legal for doctors to write off-label prescriptions. However, it is not legal for pharmaceutical companies to promote any drugs they manufacture for off-label use. They may promote the use of drugs only for the reasons the drug was approved.
Some examples of off-label prescriptions:
A drug called Neurontin (Pfizer) is approved for epileptic seizures, but may be prescribed for patients with Lou Gehrig's disease, peripheral neuropathy, or bipolar disorder.
Ketoconazole is an anti-fungal medicine, approved to treat athlete's foot, ringworm and other fungi. It may also be prescribed off-label to treat prostate cancer.