An alkaloid found in the leaves of the shrub Erythroxylon coca, which grows wild and has been cultivated in South America for thousands of years. This stimulant DRUG is commonly used for its psychoactive effects in modern times, but in fact human societies have used it for thousands of years. The custom of chewing the leaves by the native peoples of the Peruvian Andes dates back at least 5000 years. Cocaine was introduced into mainstream Western society in the last two decades of the nineteenth century, in various tonics, patent medicines, and remedies. In 1886, a Georgia pharmacist introduced what was to become the most famous drink of all time, Coca-Cola, which had extract of coca leaves. Cocaine's most famous proponent was Freud, who wrote extensively of its supposed virtues. He believed it could cure MORPHINE and ALCOHOL addiction. Not surprisingly, Freud struggled with a severe addiction to cocaine.
Cocaine induces profound changes in behaviour and psychological state as well as alterations in bodily physiology. It is administered in a variety of ways, but most commonly it is injected intravenously, snorted intranasally, or smoked in its free-base form (CRACK COCAINE). Cocaine activates the SYMPATHETIC NERVOUS SYSTEM. It is a potent vasoconstrictor and increases heart rate and blood pressure. Cocaine also induces changes in MOOD and emotional state. In general cocaine produces feelings of stimulation, well-being, vigour and EUPHORIA. Enhanced alertness, increased sexuality, heightened energy, and deepening of emotions may accompany the cocaine high. In contrast to some drugs, cocaine does not appear to alter perceptual processes or distort reality. It has been said that cocaine and other stimulants produce a neurochemical magnification of the pleasure experienced in most activities. It is clearly these positive properties that attract people to cocaine and underlie its addictive properties (see ADDICTION). However, cocaine can also induce negative emotional states and severe disruptions of behaviour. High doses of stimulants can cause DYSPHORIA and intense ANXIETY, and chronic use can result in hyper-aggressiveness, complete INSOMNIA, irritability, impulsiveness, and PANIC. Cocaine intoxication in extreme cases is characterized by PARANOIA and violent behaviour.
Cocaine is a potently reinforcing drug (see REINFORCEMENT). In fact, of all the drugs that are amenable to SELF-ADMINISTRATION by animals and humans, it may well be the most reinforcing. The cocaine addict will engage in behaviour that entails extraordinary risks to health and social stability. The extreme desire to obtain the drug has been shown in animal studies of cocaine use. Rats and monkeys rapidly acquire self-administration behaviour when given access to intravenous cocaine via a lever-press, and when forced to choose between food or cocaine, will always choose cocaine, even with lethal consequences. In the PROGRESSIVE RATIO paradigm, an animal must make progressively more responses in order to obtain intravenous cocaine reinforcement. It has been shown that a monkey will make up to 6000 presses to obtain one infusion of cocaine.
Thus, many animal studies have demonstrated that the rewarding effects produced by cocaine are indeed a powerful motivator of drug-seeking behaviour. Research suggests that cocaine (like amphetamine) is a powerful activator of the brain’s central REINFORCEMENT system. Activation of the DOPAMINE system is the primary pharmacological effect. Moreover, release of dopamine in the NUCLEUS ACCUMBENS appears to be directly linked to the rewarding properties of these drugs. Animals that have undergone lesions of the dopamine projection to the nucleus accumbens are not interested in self-administering cocaine or amphetamine. In view of the hypothesis that the nucleus accumbens may be a critical neural substrate for ‘natural’ rewards (food, sex, and so on), the notion that cocaine amplifies pleasure may actually have a neurochemical basis.
Cocaine addiction reached peak levels in the 1980s, and continues to be a major problem in many societies. Curiously, before the 1980s, cocaine was considered to be a safe, non-addicting stimulant drug. There appeared to be no overt physical symptoms that would constitute a withdrawal syndrome. The spread of crack cocaine in the 1980s changed this perception. Crack (solid, free-base cocaine) was much cheaper than powdered cocaine and became widely available, particularly to the poor. The smoking of the drug leads to a rapid, short-lasting but profound euphoria that is extremely addictive. It rapidly became clear that the criteria for SUBSTANCE DEPENDENCE DISORDER were easily met with cocaine. Compulsive use, loss of control, and a withdrawal syndrome began to be clearly recognized. Cocaine WITHDRAWAL is characterized by several phases. A triphasic abstinence pattern generally follows a cocaine binge. The first phase is termed the crash, which lasts from hours to days. The crash is characterized by a sharp decrease in mood and energy, agitation, anxiety, depression and craving for cocaine. There is an extreme need for sleep, which is usually met by the ingestion of sedatives, alcohol or opiates. The next phase, withdrawal, can last for many weeks and is characterized primarily by an intense dysphoric syndrome. Depression and ANHEDONIA (inability to experience pleasure) contrast with memories of stimulant-induced euphoria and often lead to a repetition of the bingeing cycle. If the user continues to be abstinent, the third phase emerges, extinction. During this phase, normal mood and energy are restored. However, the user may experience occasional cravings for cocaine for months or even years after the last binge. The cravings are usually invoked by stimuli or memories associated with the cocaine experience. A number of different strategies have been tried in treatment programmes, with varying outcomes. Although pharmacological strategies may be useful in achieving initial cocaine abstinence, counselling and intensive psychotherapy are important for long-term success.
Reference
Gawin F. (1991) Cocaine addiction: psychology and neurophysiology. Science 251: 1580–1585.
ANN E.KELLEY
This is the complete article, containing 927 words
(approx. 3 pages at 300 words per page).
