narcotic, drug that produces analgesia (pain relief), narcosis (state of stupor or sleep), and addiction (physical dependence on the drug). In some people narcotics also produce euphoria (a feeling of great elation). In the United States, narcotics are regulated under the Controlled Substances Act, which established a classification system with five schedules to identify drugs based on their potential for abuse, their applications in medicine, and their likelihood of producing dependence. The act is implemented by the Drug Enforcement Administration, which is empowered to prosecute violators of laws governing these controlled substances. A brief treatment of narcotics follows. For full treatment, see drug use.

The best-known narcotics are the opiates—i.e., compounds found in or derived from opium. Opium is obtained as the dried milky juice of the seed pods of the opium poppy (Papaver somniferum). Of the 20 or more alkaloids found in opium, the most important is morphine, which is primarily responsible for opium’s narcotic properties. Drugs with actions similar to morphine that are produced synthetically are known as opioids; the terms opiate, opioid, and narcotics are used interchangeably. In most countries the production, trade in, and use of narcotics are limited because of their addictive properties, detrimental effects, and the incidence of narcotic drug abuse.

Therapeutic uses

The main therapeutic use of narcotics is for pain relief, and they are in fact some of the most powerful painkillers available. When used for this purpose, they are often called narcotic analgesics. Narcotics occurring naturally in the opium poppy have been used since ancient Greek times, both for relieving pain and for producing euphoria. Extracts of the opium poppy were smoked, eaten, or drunk (as laudanum, a crude mixture of alcohol and opium). The pharmacologically active components of opium were isolated during the first half of the 19th century. The first was morphine, isolated by a young German pharmacist, F.W.A. Sertürner, in about 1804. A much milder narcotic, codeine, was in turn isolated from morphine.

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United Nations: Control of narcotics

Today narcotics are often given to patients who are dying from cancer. In this case, the drugs not only relieve pain but also seem to reduce suffering, worry, fear, and panic associated with severe pain. As terminal cancer patients often do not have long to live and the provision of an acceptable quality of life may be the paramount issue, problems of addiction are largely irrelevant.

Characteristics of addiction

The invention of the hypodermic needle in the mid-19th century allowed morphine to be administered by injection, which is useful in medicine because injections of morphine produce much greater effects than taking the same amount of drug orally. However, the availability of morphine injections led to serious problems of abuse, and laws were introduced to control the use, production, and trade of narcotics and other dangerous drugs. Such laws now exist in most countries of the world. In 1898 heroin, or diacetylmorphine, was developed from morphine by the Bayer Company in Germany. Heroin is 5 to 10 times as potent as morphine itself and is used by most narcotic addicts. Because heroin proved to be even more addictive than morphine, a search for synthetic substitutes was undertaken that resulted in such opioids as meperidine (Demerol), methadone, and levorphanol (Levo-Dromoran).

Most persistent users of heroin or other narcotics follow a classic progression from inhaling the drug to injecting it subcutaneously and then to injecting it intravenously; each of these stages usually brings a greater likelihood of addiction with it. With increasing use of the drug, euphoria and relaxation eventually give way to drug tolerance and physical dependence; the addict must use progressively larger doses to achieve the same pleasurable effects, and once the drug wears off he must endure painful symptoms of physical and psychological withdrawal. An overdose of narcotics can severely depress the central nervous system, with respiratory failure and death as a consequence.

Treatment for addiction

Probably the most effective therapy for narcotics addiction involves the synthetic opiate methadone, which, though itself addictive, blocks cravings and provides no disruptive euphoric effects of its own. Substances known as narcotic antagonists block the actions of the narcotics and reverse their effects; at narcotic receptors in the brain, narcotics act to produce their many effects, whereas narcotic antagonists block these receptors and prevent narcotics from reaching them and exerting their actions. Examples of narcotic antagonists include naloxone, naltrexone, and nalorphine. They are used to reverse the effects of an overdose of narcotics, and they can often save the life of the victim. Naloxone can be given by injection or administered as a nasal spray.

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The Editors of Encyclopaedia BritannicaThis article was most recently revised and updated by Kara Rogers.

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substance use disorder, recurrent use of drugs or alcohol that impairs psychological and physical function and undermines the affected individual’s ability to perform day-to-day activities and fulfill personal, family, or work responsibilities. Substance use disorders typically affect adolescents and adults and range from mild to severe, the more severe cases ultimately leading to addiction. Alcohol and tobacco use disorders are among the most common types of substance use disorders worldwide.

Although substances can be used occasionally with relatively small risks to mental or physical health, a substance use disorder affecting a person’s well-being and ability to carry out daily tasks can result from chronic, habitual, or patterned use. This is especially the case when individuals use substances that induce tolerance and dependence, which is common with alcohol, cannabis, cocaine, opioids, and tobacco. Repeated use of these substances is associated with changes in brain function such that neurons in the brain adapt to the substance and function normally only when the substance is present in the body. Substances become linked to pleasurable or euphoric experiences via surges of the neurotransmitter dopamine, which is part of the brain’s reward circuit. Over time, the brain develops a craving for the pleasurable or euphoric feeling, driving individuals to use the substance repeatedly.

Recurrent substance use has many different causes. For example, some persons may be genetically predisposed to substance use and addiction. In other cases, underlying psychiatric conditions, such as anxiety or depression, or factors such as environmental or social stressors, including exposure to drugs in adolescence and peer pressure, may influence whether or the extent to which a person uses a substance. Adverse childhood experiences, such as sexual abuse, may also have a role. Persons with substance use disorders can exhibit a wide range of symptoms. Examples include abnormal movements, altered thinking, changes in personality, inability to make decisions, poor judgment, social withdrawal, and sudden changes in mood.

Substance use disorders are diagnosed through evaluation of medical history and behaviours that suggest recurring substance use, as well as through drug testing and prescription drug monitoring. A diagnosis of mild substance use disorder is generally based on the presence of two or more signs or symptoms for a period of at least 12 months, whereas severe cases are diagnosed when the individual exhibits six or more symptoms. Treatment is tailored to the individual. Recovery from substance use disorder may involve detoxification, where the individual gradually stops using the substance, allowing it to clear from the body in a way that minimizes symptoms of withdrawal. Cognitive and behavioral therapies may be used to help individuals unlearn negative behaviours and adopt healthier habits. Medications may also be used to help modify neurotransmitter levels and activity in the brain.

Kara Rogers