Drugs

 Encyclopædia Britannica ||
 * =drug =

Until the mid-19th century the approach to drug therapeutics was entirely empirical. This thinking changed when the mechanism of drug action began to be analyzed in physiological terms and when some of the first chemical analyses of naturally occurring drugs were performed. The end of the 19th century signaled the growth of the pharmaceutical industry and the production of the first synthetic drugs. Chemical synthesis has become the most important source of therapeutic drugs, although genetic engineering is developing as a means of synthesizing proteins.Any chemical substance that affects the functioning of living things and the organisms (such as bacteria, fungi, and viruses) that infect them. Pharmacology, the science of drugs, deals with all aspects of drugs in medicine, including their mechanism of action, physical and chemical properties, metabolism, therapeutics, and toxicity. This article focuses on drugs used in the treatment and prevention of human diseases. For a discussion of the nonmedical use of drugs, //see// drug use. Drugs produce harmful as well as beneficial effects, and decisions about when and how to use them therapeutically always involve the balancing of benefits and risks. Drugs approved for human use are divided into those available only with a prescription and those that can be bought freely over the counter. The availability of drugs for medical use is regulated by law. Drug treatment is the most frequently used type of therapeutic intervention in medicine. Its power and versatility derive from the fact that the human body relies extensively on chemical communication systems to achieve integrated function among billions of separate cells. The body is, therefore, highly susceptible to the calculated chemical subversion of parts of this communication network that occurs when drugs are administered.

Encyclopædia Britannica, Inc., 2011. Web. 12 Sept. 2011.
 * drug .**" //Encyclopædia Britannica//. //Encyclopædia Britannica Online Library Edition//.

 Encyclopædia Britannica ||
 * =drug abuse=

The excessive, maladaptive, or addictive use of drugs for nonmedical purposes despite social, psychological, and physical problems that may arise from such use. Abused substances include such agents as anabolic steroids, which are used by some athletes to accelerate muscular development and increase strength and which can cause heart disease, liver damage, and other physical problems; and psychotropic agents, substances that affect the user's mental state and are used to produce changes in mood, feeling, and perception. The latter category, which has a much longer history of abuse, includes opium (and such derivatives as heroin), hallucinogens, barbiturates, cocaine, amphetamines, tranquilizers, the several forms of cannabis, and alcohol. A brief treatment of drug abuse follows. For full treatment, //see// drug use. //See also// steroid. The history of nonmedical drug consumption is ancient. The discovery of the mood-altering qualities of fermented fruits and substances such as opium has led to their use and, often, acceptance into society. Just as alcohol has a recognized social place in the West, so many other psychotropics have been accepted in different societies.

The major problem that arises from the consumption of psychotropic drugs is dependence, the compulsion to use the drug despite any deterioration in health, work, or social activities. Dependence varies from drug to drug in its extent and effect; it can be physical or psychological or both. Physical dependence becomes apparent only when the drug intake is decreased or stopped and an involuntary illness called the withdrawal (or abstinence) syndrome occurs. Drugs known to produce physical dependence are the opiates (i.e., opium and its derivatives) and central-nervous-system depressants such as barbiturates and alcohol. Psychological dependence is indicated when the user relies on a drug to produce a feeling of well-being. This type of dependence varies widely with both substance and user. In its most intense form the user becomes obsessed with the drug and focuses virtually all his interest and activity on obtaining and using it. Another related phenomenon is tolerance, a gradual decrease in the effect of a certain dose as the drug is repeatedly taken; increasingly larger doses are needed to produce the desired effect. Tolerance does not always develop. It is most marked with habitual opiate users. The term addiction is often used synonymously with dependence but should probably be reserved for drugs known to cause physical dependence. Other hazards of drug abuse include general risks, such as the danger of infection by the AIDS virus and other diseases that can be communicated by use of nonsterile needles or syringes when drugs are taken by injection. Some hazards are associated with the specific effects of the particular drug—paranoia with high doses of stimulants, for example. In addition, adverse social effects stemming from drug abuse are numerous. Heroin, an opiate that is not used medically in the United States, is one of the drugs most associated with abuse and addiction in the eyes of the public. In general, opiates are called narcotics because they are used medically to relieve pain and produce sleep. Other opiates that have been abused are opium, morphine, pethidine, codeine, dipipanone, and methadone. Methadone is often used in substitution therapy as a less-addictive opiate that, theoretically at least, can be used to wean the user off heroin and eventually off opiates altogether. Drugs that either depress or stimulate the central nervous system have long been used for nonmedical reasons. Depressants include all sedatives and hypnotics such as barbiturates and benzodiazepines (minor tranquilizers). These are usually taken by mouth but can be injected. The main stimulants are amphetamines or their derivatives and cocaine, a natural component of the leaves of the coca plant. Amphetamines can be taken by mouth or injected; cocaine is either injected or inhaled through the nose. One form of cocaine (freebase, or crack) is generally smoked. Other drugs that are frequently abused include cannabis (marijuana, hashish, etc., from the hemp plant //Cannabis sativa//), PCP, and such hallucinogens, or psychedelics, as LSD and mescaline. The purchase, sale, and nonmedical consumption of all the aforementioned drugs are illegal, and these psychotropic drugs can be obtained only on the black market. However, this is not the only route to drug abuse. Alcohol, for instance, can be legally purchased throughout much of the world, despite its high potential for abuse. Also, dependence on prescribed drugs is not uncommon, especially with tranquilizers and hypnotics. What was once a serious social problem of dependence on prescribed barbiturates has been overtaken largely by the widespread use of benzodiazepine tranquilizers such as diazepam (Valium) and chlordiazepoxide (Librium). Millions of legal prescriptions for these drugs are issued every year. Problems relating to drug abuse can also occur with substances not normally thought of as drugs. Solvent abuse, commonly known as “glue-sniffing,” is a growing problem, especially among teenagers and even younger children. The inhalation of volatile solvents produces temporary euphoria but can lead to death by respiratory depression, asphyxiation, or other causes. > Encyclopædia Britannica, Inc., 2011. Web. 12 Sept. 2011.
 * " **drug abuse .**" //Encyclopædia Britannica//. //Encyclopædia Britannica Online Library Edition//.