Chapter 2 - Characteristics and Classification of Substances

Abstract

This chapter describes the characteristics and classification of substances of abuse. The different classes of substance of abuse discussed in this chapter include: depressants; stimulants, cannabinoids; nicotine; opioids; steroids, and hallucinogens. The effect of a drug depends on dosage, potency, composition, frequency of use, method of use, the presence of other substances, and physiology. The dose–response relationship is explained in terms of an adequate dose required for threshold or experienced effect. As dosage is increased, there is a commensurate effect until the maximum effect is reached that is determined physiologically. Drug potency determines the amount of the drug necessary to produce a certain effect, and it is determined by affinity and efficacy. Drug affinity refers to the drug's ability to bind to the receptor's site of action. Method of use of drug is the manner in which a drug is administered that affect the onset of effects, peak effects, and duration of effects. Frequency of use of drug significantly impacts drug effects in two main ways: (1) frequent use of drug increases physiological and psychological changes and (2) accumulation of drug or its metabolic byproducts can take place, if there is a high frequency of drug use. The chapter also briefly describes the therapeutic effect, adverse reactions, allergic reaction, idiosyncratic reactions, and toxic effects of drugs.