What is the term for using an FDA approved drug for a purpose not officially approved?

The term for using an FDA-approved drug for a purpose not officially approved is "off-label." This practice occurs when healthcare professionals prescribe medications for conditions or in dosages that differ from those approved by the FDA. Off-label use is relatively common and can occur for several reasons, such as the availability of data supporting the drug's effectiveness for a different condition or the need to find alternative treatments when no approved options exist.

Such use is legal and can be based on scientific research or clinical experience, but it may carry risks, as the safety and efficacy of the drug for the unapproved use might not have been fully evaluated in clinical trials. While the other terms relate to drug usage in different contexts, they do not specifically refer to the practice of using approved medications outside their labeled indications.