Nearly any drug used to treat illness also poses certain risks. One such risk, generally limited to drugs that act on the central nervous system, is that the drug will be abused because of those effects. Such a drug is said to have "abuse potential" or "abuse liability." If it has important medicinal uses, it may still be available by prescription, but legal controls will be placed on how it can be prescribed. New drugs are tested to determine their potential for abuse so that both the public and the medical profession can be warned about the need for appropriate caution when using them.

Conducting tests on humans serves several purposes in the development of safer and more effective drugs. When research done on laboratory animals shows that a drug might have abuse potential...