Overview of drugs

[Lizzy Liz]

A drug is defined by U.S. law as any substance (other than a food or device) intended for use in the diagnosis, cure, relief, treatment, or prevention of disease or intended to affect the structure or function of the body. (Oral contraceptives are an example of drugs that affect the function of the body rather than a disease.) This comprehensive definition of a drug, although important for legal purposes, is rather complex for everyday use. A simpler but workable definition of a drug is any chemical or biologic substance that affects the body and its processes.
Some people incorrectly use the word drug to mean only a substance that produces a pleasurable sensation. The excessive and persistent use of mind-altering substances without medical need has accompanied the appropriate medical use of drugs throughout recorded history. Some of the drugs that fall into this category have legitimate medical purposes, and others do not (see Overview of Substance-Related Disorders).