Because of the popularity of the amphetamines and the ease with which they can be procured, instances of acute and chronic intoxication are not uncommon. Methamphetamine is the most frequently abused in this category, as intravenous “crystal” or smoked as “ice.” The toxic signs are essentially an exaggeration of the activating effects— restlessness, excessive speech and motor activity, tremor, and insomnia. Severe intoxication gives rise to hallucinations, delusions, and changes in affect and thought processes—a state that may be indistinguishable from paranoid schizophrenia. An amphetamine-associated vasculopathy and intracerebral and subarachnoid hemorrhage are well recognized but rare complications of chronic or acute intoxication (Harrington et al and Chap. 33). Similar cerebrovascular complications may appear with sympathomimetic agents contained in over-the-counter cold medications and in dieting aids. Phenylpropanolamine has been implicated most often but ephedrine, cocaine (see below), and similar agents rarely have the same effects and induce a vasculopathy. The pathogenesis of the vascular lesion is unknown (both vasospasm and arteritis have been reported).
Chronic use of amphetamines can lead to a high degree of tolerance and psychologic dependence. Withdrawal of the drug after sustained oral or intravenous use is regularly followed by a period of prolonged sleep (a disproportionate amount of which is rapid eye movement [REM] sleep), from which the patient awakens with a ravenous appetite, muscle pains, and feelings of profound fatigue and depression. Treatment consists of discontinuing the use of amphetamine and administering antipsychosis drugs. Hypertension may need to be treated until the effect of the drug has waned.
The conventional use of cocaine as a local anesthetic has for many years been overshadowed by its illicit and widespread use as a stimulant and mood elevator. Cocaine is abused intranasally (“snorted”), smoked, or injected intravenously or intramuscularly. There has been an alarming escalation in the use of cocaine, mainly because a relatively pure and inexpensive form of the free alkaloid base (“crack”) became readily available in the 1980s. This form of cocaine is heat-stable and therefore suitable for smoking. According to the National Household Survey on Drug Abuse, there are an estimated 600,000 frequent cocaine users in the United States. (Frequent use was arbitrarily defined as use on 51 or more days during the preceding year.) The number of occasional users (less than 12 days in the preceding year) was 2.4 million. These figures are probably subject to significant underreporting.
A sense of well-being, euphoria, loquacity, and restlessness are the familiar effects. Pharmacologically, cocaine is thought to act like the tricyclic antidepressants; that is, it blocks the presynaptic reuptake of biogenic amines, thus producing vasoconstriction, hypertension, and tachycardia and predisposing to generalized tremor, myoclonus, seizures, and psychotic behavior. It has an additional weaker action, similar to amphetamines, of causing the release of endogenous monoamines. The cocaine abuser readily develops psychologic dependence and habituation, that is, an inability to abstain from frequent compulsive use. The manifestations of physical dependence are more subtle and difficult to recognize. Nevertheless, abstinence from cocaine following a period of chronic abuse is regularly attended by insomnia, restlessness, anorexia, depression, hyperprolactinemia, and signs of dopaminergic hypersensitivity—a symptom complex that constitutes an identifiable withdrawal syndrome.