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Drug abuse is usually taken to mean the use of an illicit drug or the excessive or nonmedical use of a licit drug. It also denotes the deliberate use of chemicals that generally are not considered drugs by the lay public but may be harmful to the user. A primary motivation for drug abuse appears to be the anticipated feeling of pleasure derived from the CNS effects of the drug. The older term "physical (physiologic) dependence" is now generally denoted as dependence, whereas "psychological dependence" is more simply called addiction.
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Dopamine in the mesolimbic system appears to play a primary role in the expression of "reward," but excessive dopaminergic stimulation may lead to pathologic reinforcement such that behavior may become compulsive and no longer under control—common features of addiction. Though not necessarily the only neurochemical characteristic of drugs of abuse, it appears that most addictive drugs have actions that include facilitation of the effects of dopamine in the CNS.
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The sedative-hypnotic drugs are responsible for many cases of drug abuse. The group includes ethanol, barbiturates, and benzodiazepines. Benzodiazepines are commonly prescribed drugs for anxiety and, as Schedule IV drugs, are judged by the US government to have low abuse liability (Table 32–1). ...