In the United States, the majority of medications and legal drugs must gain approval from the ]U.S. Food and Drug Administration (FDA) before they can be prescribed to the public. The FDA approval process often takes years and can cost millions, or even hundreds of millions, for the drug's producer. Once the FDA approves a drug, it's granted approval status only for specific conditions, or indications. Any use beyond these indications is considered off-label use [source: American Cancer Society].
While it's perfectly legal for doctors to prescribe drugs for off-label conditions, the makers of these drugs must take extreme caution when it comes to selling and marketing these medications in accordance with FDA standards. Companies who market drugs for off-label uses are subject to criminal and civil penalties from the FDA, the U.S. Department of Justice and any number of other organizations.
Despite these rigid standards, as many as 20 percent of prescriptions are for off-label uses. This figure can be even higher for cancer and psychosis medications [source: Surrey]. Read on to learn about some of the most popular drugs prescribed for unique purposes in the U.S.