When the Food and Drug Administration (FDA) approves a new medication, it is because the product has been subjected to rigorous clinical testing and is deemed safe and effective for the treatment of the specific disorder/condition for which it was designed. It does not mean the drug is completely free of potentially dangerous side effects.
What it does mean is that after long and careful evaluation, scientists at the agency have determined that the benefits to a patient with a specific condition outweigh the risks. Formal FDA approval for a given drug is limited to that for which it has been designed to treat.
This said, a physician may legally prescribe a drug for an unapproved use if, in his/her considered professional judgment, the drug will help a patient's condition. This is usually done after other treatments intended for a patient's problem have been ineffective, or there are no other alternatives readily available.
It’s illegal for a drug manufacturer or distributor to market a product for any use other than that for which it was approved by FDA. When they do, it is referred to as an “off-label” promotion. This has become a significant problem since 1985 when the FDA began allowing direct-to-consumer (DTC) advertising of drugs, which is very popular today. In 2015, spending on DTC ads in the US reached $5.6 billion.
Patients whose physicians recommend off-label prescriptions for their conditions should consider a number of issues, such as the original approved use of the medication and whether or not there are any approved alternatives. Before taking an off-label medication, one should also find out if there have been any clinical studies to support the use of the drug for treating their condition and learn as much as possible about the risks and potential side effects.
It should also be noted that insurers may not cover the costs of an off-label prescription. Patients should perform due diligence and discuss all alternatives with their health care provider before agreeing to take such medications.