Drugs of Abuse: Their Actions & Potential Hazards
 Author:   Samuel Irwin, Ph.D.
Publisher:   Do It Now Foundation

 Publication Date:

  September 2003

 Catalog No:


Chapter 2: Defining Terms

Throughout the text, we'll be using a number of specialized terms and expressions that you may know better by other, "everyday" meanings.

To minimize confusion, we'll define terms this way:

Drug: Any non-nutritional chemical that alters body functions, producing physical, psychological, or behavioral change.

Psychoactive Drug: A natural or synthetic substance that affects mental processes or alters mood or behavior.

Drug Use: The intake of a chemical substance, whether or not the substance is used medically or legally.

Drug Abuse: The intake of a chemical substance under circumstances or at dosage levels that significantly increase risks of harm, whether or not the substance is licit or illicit.

Psychological Dependence: A tendency for repeated or compulsive use of a chemical, or involvement in an activity, because its effects are considered pleasurable or satisfying, or because it reduces undesirable feelings. A person may be psychologically dependent on drugs, food, television, sex, relationships, or recreational activities.

A further distinction can be drawn between gratification dependence, in which major withdrawal symptoms are generally minor or absent, and emotional dependence, in which serious withdrawal symptoms appear after use stops.

Physical Dependence: Adaptation of body tissues to the continued presence of a chemical, revealed in the form of serious, even life-threatening withdrawal symptoms. The extent of physical dependence and the severity of withdrawal symptoms can vary, from drug to drug, and by amount, frequency, and duration of use.

Tolerance: Development of body resistance to the effects of a chemical so that larger doses are required to reproduce the original effect. When tolerance develops rapidly (as with LSD), the user may be forced to stop use until tissues regain their responsiveness.

When tolerance develops slowly and the chemical also produces physical dependence (e.g. heroin, alcohol), the increased dose requirements speed up and intensify the development of physical dependence.

Addiction: A state of chemical abuse characterized by a high level of physical and/or psychological dependence.

When an addicting substance is abruptly stopped, withdrawal symptoms appear and additional doses are necessary to ease those symptoms or to produce the original effects.

A hallmark of addiction is continued, compulsive use despite serious consequences -- such as health problems and the loss of job or family.


Classifying Drugs

An endless number of schemes could be (and have been, in fact) designed to classify the many drugs of abuse. Each grouping has its own strengths and weaknesses, but none ever sorts all substances into "perfect" categories.

We've chosen a relatively straightforward model that lumps substances into three simple categories: "over-the-counter drugs," "prescription drugs," and "street drugs."

This is not to imply that drugs exist in only one category or another. There's a great deal of movement across even the lines we've selected. For example, the nonprescription stimulants caffeine and phenylpropanolamine are listed alongside their chemical cousin methamphetamine in the "street drugs" category, to avoid endless redundancy and because of space limitations in the booklet format.

In the same way, narcotic analgesics are listed as "prescription drugs," although they're commonly bought and sold on the street, since treatment of pain is their primary purpose.

Still, and in spite of the confusion factor, we hope that what follows is a workable guide to the relative risks of common drugs of abuse.

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Read On! Chapter 3: Over-the-Counter Drugs

This is one in a series of publications on drugs, behavior, and health published by Do It Now Foundation. Check us out online at www.doitnow.org.