Aspirin is technically an NSAID, but the term is often used to refer to nonaspirin products. The first nonaspirin NSAIDs were introduced in 1964. Common NSAID products include diclofenac (Cataflam, Voltaren), piroxicam (Feldene), and indomethacin (Indocin). acetaminophen, ibuprofen, naproxen, and ketoprofen are available as over-the-counter drugs in the United States. The cox-2 inhibitors, such as celecoxib (Celebrex), selectively inhibit clooxygenase-2 (cox-2), an enzyme that causes pain and inflammation in arthritic joints, but do not interfere with cox-1, which protects the stomach and intestinal lining from ulceration. Very common drugs, NSAIDs are taken daily by an estimated 3 million Americans.

Although they are often considered easier to tolerate than aspirin, and most do not have as strong an anticlotting effect as aspirin, NSAIDS can have serious side effects, particularly gastrointestinal ulcers and upper gastrointestinal tract bleeding and perforation in those who take the drugs on a regular basis. NSAID-related gastropathy results in more than 2,000 deaths in the United States each year.

Hallucinogens have been used for centuries by certain peoples. The Hindus and the Aztecs used them to facilitate meditation, cure illness, and enhance mystical powers. Many North American tribal peoples still use hallucinogenic mushrooms and peyote in tribal rituals.

Effects

Hallucinogens produce a wide range of effects, depending on the properties, dosage, and potency of the drug, the personality and mood of the drug taker, and the immediate environment. Visually, perception of light and space is altered, and colors and detail take on increased significance. If the eyes are closed the drug taker often sees intense visions of different kinds. Nonexistent conversations, music, odors, tastes, and other sensations are also perceived. The sensations are often either very pleasant or very distasteful and disturbing. The drugs frequently alter the sense of time and cause feelings of emptiness. For many individuals the separation between self and environment disappears, leading to a sense of oneness or holiness.

The effects, sometimes referred to as a "trip," can last from an hour to a few days. "Bad trips," full of frightening images, monsters, and paranoid thoughts are known to have resulted in accidents and suicides. Flashbacks (unexpected reappearances of the effects) can occur months later.

Physiologically, the drugs act as mild stimulants of the sympathetic nervous system, causing dilation of the pupils, constriction of some arteries, a rise in blood pressure, and increased excitability of certain spinal reflexes. Many hallucinogenic drugs share a basic chemical structural unit, the indole ring, which is also found in the nervous system substance serotonin. Mescaline has chemical similarities to both the indole ring and the adrenal hormone epinephrine.

There are generic versions of both over-the-counter and prescription medications, but not all drugs have generic equivalents. Generic drugs can only be produced when a patent on a brand name drug expires or when a patent has never existed. They are generally cheaper than the equivalent brand name drug because of much lower marketing and development costs. Because a generic competitor can hurt a brand name manufacturer's profits, drug companies have used legal action and regulatory delays to slow the introduction of generics, or have paid generic manufacturers to postpone the production and marketing of generics. The Medicare overhaul legislation passed in 2003 contained sections designed to speed the introduction of generic drugs by making it easier to challenge weak or invalid drug patents.

The most common cause of female infertility is failure to ovulate. In certain cases this can be corrected with the drug clomiphene citrate (Clomid, Serophene). Introduced in 1967, clomiphene stimulates the release of the gonadotropic hormones: follicle-stimulating hormone (FSH) and luteinizing hormone (LH). FSH functions to stimulate the ovarian follicle (the egg and its surrounding fluid and hormones); LH triggers ovulation. In some studies, clomiphene has been associated with an increased risk of ovarian cancer. Clomiphene is also used to stimulate spermatogenesis in men with low sperm counts.

Human menopausal gonadotropin, or menotropin (Pergonal), introduced in 1970, is an extract from the urine of menopausal women. It contains FSH and LH and encourages ovulation. It is often given together with human chorionic gonadotropin (HCG), a hormone secreted by the placenta during pregnancy and obtained from the urine of pregnant women. Its action is similar to that of luteinizing hormone. In males the same combination is given to increase testosterone production, which in turn increases sperm production.

Urofollitropin (Metrodin) is essentially follicle-stimulating hormone without luteinizing hormone. It is used especially in women with polycystic ovary syndrome, who tend to have too little FSH and too much LH. A frequent result of ovulation induced by these drugs is the production of more than one ovum (egg) in a month, and subsequent multiple births.

Progesterone is a female sex hormone that induces secretory changes in the lining of the uterus essential for successful implantation of a fertilized egg. It is released by the ovary after the ovum is released. It is administered in cases where fertilization of the ovum does occur but where there is evidence that the uterine lining is unable to support the developing fetus, as in repeated miscarriages or bleeding during pregnancy.

See also DES (diethylstilbestrol).

The number of drug-resistant bacterial strains has increased in part because of the indiscriminate use of antibiotics, which have sometimes been overprescribed. Such misuse speeds the process by destroying bacteria that would compete with resistant strains. In addition, patients sometimes stop treatment when they start to feel better, leaving a residual population of bacteria that is likely to be more resistant to drug treatment. Another source of resistance is the routine use of antibiotics in animal feed to enhance growth, a practice that has led to resistant strains of Escherichia coli and Salmonella that have been passed on to consumers. The presence of drugs in the water supply, due at least in part to human and animal excretion and the disposal of unused drugs, is also believed to contribute to drug resistance in bacteria.

Resistance is due to random genetic mutations in the bacterial cell that alter its sensitivity to a single drug or to chemically similar drugs through a variety of mechanisms. Many bacteria can transfer their resistance to other bacteria of the same or different species. Resistance has occurred in common infectious bacteria such as pneumococcus (a cause of pneumonia, meningitis, and childhood ear infections) and enterococcus (a cause of wound infections). It has also occurred in such diseases as malaria and tuberculosis. Concerns are increasing as strains develop resistance to multiple drugs, including even the most powerful antibiotics (e.g., vancomycin). Although drug companies are again concentrating on antibiotic research, no new products are expected until the turn of the century, and many infectious-disease experts are urging that doctors consider the public health risk before prescribing antibiotics and that the government regulate the use of antibiotics in agriculture.

Definitions of drug abuse and addiction are subjective and infused with the political and moral values of the society or culture. For example, the stimulant caffeine in coffee and tea is a drug used by millions of people, but because of its relatively mild stimulatory effects and because caffeine does not generally trigger antisocial behavior in users, the drinking of coffee and tea, despite the fact that caffeine is physically addictive, is not generally considered drug abuse. Even narcotics addiction is seen only as drug abuse in certain social contexts. In India opium has been used for centuries without becoming unduly corrosive to the social fabric.

The United States has the highest substance abuse rate of any industrialized nation. Government statistics (1997) show that 36% of the United States population has tried marijuana, cocaine, or other illicit drugs. By comparison, 71% of the population has smoked cigarettes and 82% has tried alcoholic beverages. Marijuana is the most commonly used illicit drug.

Types of Abused Substances

There are many levels of substance abuse and many kinds of drugs, some of them readily accepted by society.

Legal substances, approved by law for sale over the counter or by doctor's prescription, include caffeine, alcoholic beverages (see alcoholism), nicotine (see smoking), and inhalants (nail polish, glue, inhalers, gasoline). Prescription drugs such as tranquilizers, amphetamines, benzodiazepines, barbiturates, steroids, and analgesics can be knowingly or unknowingly overprescribed or otherwise used improperly. In many cases, new drugs prescribed in good conscience by physicians turn out to be a problem later. For example, diazepam (Valium) was widely prescribed in the 1960s and 70s before its potential for serious addiction was realized. In the 1990s, sales of fluoxetine (Prozac) helped create a $3 billion antidepressant market in the United States, leading many people to criticize what they saw as the creation of a legal drug culture that discouraged people from learning other ways to deal with their problems. At the same time, readily available but largely unregulated herbal medicines have grown in popularity; many of these are psychoactive to some degree, raising questions of quality and safety. Prescription drugs are regulated by the Food and Drug Administration and the Drug Enforcement Administration.

Prescription drugs are considered illegal when diverted from proper use. Some people shop until they find a doctor who freely writes prescriptions; supplies are sometimes stolen from laboratories, clinics, or hospitals. Morphine, a strictly controlled opiate, and synthetic opiates, such as fentanyl, are most often abused by people in the medical professions, who have easier access to these drugs. Other illegal substances include cocaine and crack, marijuana and hashish, heroin, hallucinogenic drugs such as LSD, PCP (phencycline or "angel dust"), "designer drugs" such as MDMA (Ecstasy), and "party drugs" such as GHB (gamma hydroxybutyrate).

Motivations for Drug Use

People take drugs for many reasons: peer pressure, relief of stress, increased energy, to relax, to relieve pain, to escape reality, to feel more self-esteem, and for recreation. They may take stimulants to keep alert, or cocaine for the feeling of excitement it produces. Athletes and bodybuilders may take anabolic steroids to increase muscle mass.

Effects of Substance Abuse

The effects of substance abuse can be felt on many levels: on the individual, on friends and family, and on society.

People who use drugs experience a wide array of physical effects other than those expected. The excitement of a cocaine high, for instance, is followed by a "crash": a period of anxiety, fatigue, depression, and an acute desire for more cocaine to alleviate the feelings of the crash. Marijuana and alcohol interfere with motor control and are factors in many automobile accidents. Users of marijuana and hallucinogenic drugs may experience flashbacks, unwanted recurrences of the drug's effects weeks or months after use. Sudden abstinence from certain drugs results in withdrawal symptoms. For example, heroin withdrawal can cause vomiting, muscle cramps, convulsions, and delirium. With the continued use of a physically addictive drug, tolerance develops; i.e., constantly increasing amounts of the drug are needed to duplicate the initial effect. Sharing hypodermic needles used to inject some drugs dramatically increases the risk of contracting AIDS and some types of hepatitis. In addition, increased sexual activity among drug users, both in prostitution and from the disinhibiting effect of some drugs, also puts them at a higher risk of AIDS and other sexually transmitted diseases. Because the purity and dosage of illegal drugs are uncontrolled, drug overdose is a constant risk. There are over 10,000 deaths directly attributable to drug use in the United States every year; the substances most frequently involved are cocaine, heroin, and morphine, often combined with alcohol or other drugs. Many drug users engage in criminal activity, such as burglary and prostitution, to raise the money to buy drugs, and some drugs, especially alcohol, are associated with violent behavior.

The user's preoccupation with the substance, plus its effects on mood and performance, can lead to marital problems and poor work performance or dismissal. Drug use can disrupt family life and create destructive patterns of codependency, that is, the spouse or whole family, out of love or fear of consequences, inadvertently enables the user to continue using drugs by covering up, supplying money, or denying there is a problem. Pregnant drug users, because of the drugs themselves or poor self-care in general, bear a much higher rate of low birth-weight babies than the average. Many drugs (e.g., crack and heroin) cross the placental barrier, resulting in addicted babies who go through withdrawal soon after birth, and fetal alcohol syndrome can affect children of mothers who consume alcohol during pregnancy. Pregnant women who acquire the AIDS virus through intravenous drug use pass the virus to their infant.

Drug abuse affects society in many ways. In the workplace it is costly in terms of lost work time and inefficiency. Drug users are more likely than nonusers to have occupational accidents, endangering themselves and those around them. Over half of the highway deaths in the United States involve alcohol. Drug-related crime can disrupt neighborhoods due to violence among drug dealers, threats to residents, and the crimes of the addicts themselves. In some neighborhoods, younger children are recruited as lookouts and helpers because of the lighter sentences given to juvenile offenders, and guns have become commonplace among children and adolescents. The great majority of homeless people have either a drug or alcohol problem or a mental illness—many have all three.

The federal government budgeted $17.9 billion on drug control in 1999 for interdiction, prosecution, international law enforcement, prisons, treatment, prevention, and related items. In 1998, drug-related health care costs in the United States came to more than $9.9 billion.

Treatment

Treatment of substance abusers depends upon the severity and nature of the addiction, motivation, and the availability of services. Some users may come into treatment voluntarily and have the support of family, friends, and workplace; others may be sent to treatment by the courts against their will and have virtually no support system. Most people in drug treatment have a history of criminal behavior; approximately one third are sent by the criminal justice system.

Both pharmacological and behavioral treatments are used, often augmented by educational and vocational services. Treatment may include detoxification, therapy, and support groups, such as the 12-step groups Alcoholics Anonymous, Narcotics Anonymous, and Cocaine Anonymous. Nonresidential programs serve the largest number of patients. Residential facilities include hospitals, group homes, halfway houses, and therapeutic communities, such as Phoenix House and Daytop Village; most of the daily activities are treatment-related. Programs such as Al-Anon, CoAnon, and Alateen, 12-step programs for family and friends of substance abusers, help them to break out of codependent cycles.

Some treatment programs use medicines that neutralize the effects of the drug. Antabuse is a medicine used in the treatment of alcoholism. It causes severe and sudden reaction (nausea, vomiting, headache) when alcohol is present. Naltrexone, to treat alcohol and heroin abuse, and acamprosate, used to treat alcoholism, both reduce cravings. Other programs use stabilizing medications, e.g., methadone or buprenorphine maintenance programs for heroin addiction. Acupuncture has been successful in treating the cravings that accompany cocaine withdrawal and is being used with pregnant substance abusers to improve the health of their babies.

For every person in drug treatment there are an estimated three or four people who need it. Many who attempt to get treatment, especially from public facilities, are discouraged by waits of over a month to get in. Evaluating the effectiveness of treatment is difficult because of the chronic nature of drug abuse and alcoholism and the fact that the disease is usually complicated by personal, social, and health factors.

Fighting Substance Abuse

Efforts at fighting substance abuse are dictated by the attitudes of the public and their perceptions of a substance's dangers. These attitudes may be framed by personal experience, media portrayals, news events, or drug education. Most drug enforcement is local, but the international and interstate nature of the drug trade has gradually resulted in more federal involvement. The Drug Enforcement Administration (DEA), created in 1973, is responsible for enforcing federal laws and policies and coordinates information sharing between agencies. Approaches to combating the drug problem have traditionally focused on reducing both supply and demand.

The policy of supply reduction aims to decrease the available amount of a drug and make its cost prohibitively high due to the short supply. One strategy for supply reduction is the passage and enforcement of strict laws that govern the prescribing of narcotic drugs. Other strategies are aimed at disrupting drug trafficking. In general, heroin and the other opiates come into the United States from SW and SE Asia, Central America, and Colombia, cocaine from South America, marijuana from domestic sources, Mexico, Colombia, and Jamaica, and designer drugs from domestic clandestine laboratories. The Bureau of Immigration and Customs Enforcement is charged with interdicting smuggled drugs that come in across land borders, the U.S. Coast Guard with interdiction on the seas. Other attempts to disrupt the flow of drugs involve the seizure of clandestine labs, arrest and conviction of drug dealers and middlemen, and international efforts to break up drug cartels and organized crime distribution networks. Asset seizure is a controversial but effective strategy that allows authorities to confiscate any profits derived from or property used in drug trafficking, including cars, houses, and legal fees paid to defense attorneys. Eradication of crops was the strategy behind the spraying of paraquat on Mexican marijuana crops in the 1970s. Some attempts at reducing drug production by creating more lucrative markets for nondrug crops in drug-producing areas also have been made.

Attempts to reduce the demand for drugs in the main involve education and treatment. For the most part, responsibility for education falls to local schools and for treatment to local public hospitals or private treatment centers. The federal government gathers statistics and provides funds for treatment and rehabilitation programs. Certain laws are designed to promote education of the public (e.g., those requiring warning labels on cigarettes and alcoholic beverages), and all states have Driving While Intoxicated (DWI) laws. Other drug laws attempt to reduce the demand for drugs by imposing stiff penalties for drug possession, manufacture, and trafficking. Drug testing in the workplace has been a controversial measure, weighing productivity and the safety of the workers and those for whom they are responsible against an individual's right to privacy, but it has resulted in increased public awareness. Some grassroots groups have had a profound effect; MADD (Mothers Against Drunk Driving) was instrumental in raising the drinking ages in many states.

Legalization and Decriminalization

The concept of controlling drugs is a relatively recent phenomenon, and one that has been met with limited success despite the billions of dollars spent. Some people argue that if drugs were legalized (as occurred with the repeal of Prohibition), drug trafficking and the violence it engenders would disappear. Some contend also that with government regulation dosages would be standardized and dangerous contaminants eliminated, making drugs safer. It has also been suggested that resulting lower prices for drugs would preclude the need for criminal activity to raise money for their purchase, and that billions of dollars saved from supply reduction programs could be put toward education and treatment. Nevertheless, a substantial majority of Americans polled have thought legalization a bad idea. Those opposed to legalization believe that removal of deterrents would encourage drug use, that people would still steal to buy drugs, and that many drugs are so inexpensive to produce that there would still be a black market.

Decriminalization is the elimination or reduction of criminal penalties for using or dealing in small amounts of certain drugs. Attitudes toward decriminalization change with the times and with actual and perceived dangers involved. Many localities decriminalized marijuana in the 1970s—and many reinstituted stricter laws in the 1980s.

History

Humans have used drugs of one sort or another for thousands of years. Wine was used at least from the time of the early Egyptians; narcotics from 4000 B.C.; and medicinal use of marijuana has been dated to 2737 B.C. in China. But not until the 19th cent. A.D. were the active substances in drugs extracted. There followed a time when some of these newly discovered substances—morphine, laudanum, cocaine—were completely unregulated and prescribed freely by physicians for a wide variety of ailments. They were available in patent medicines and sold by traveling tinkers, in drugstores, or through the mail. During the American Civil War, morphine was used freely, and wounded veterans returned home with their kits of morphine and hypodermic needles. Opium dens flourished. By the early 1900s there were an estimated 250,000 addicts in the United States.

The problems of addiction were recognized gradually. Legal measures against drug abuse in the United States were first established in 1875, when opium dens were outlawed in San Francisco. The first national drug law was the Pure Food and Drug Act of 1906, which required accurate labeling of patent medicines containing opium and certain other drugs. In 1914 the Harrison Narcotic Act forbade sale of substantial doses of opiates or cocaine except by licensed doctors and pharmacies. Later, heroin was totally banned. Subsequent Supreme Court decisions made it illegal for doctors to prescribe any narcotic to addicts; many doctors who prescribed maintenance doses as part of an addiction treatment plan were jailed, and soon all attempts at treatment were abandoned. Use of narcotics and cocaine diminished by the 1920s. The spirit of temperance led to the prohibition of alcohol by the Eighteenth Amendment to the Constitution in 1919, but Prohibition was repealed in 1933.

In the 1930s most states required antidrug education in the schools, but fears that knowledge would lead to experimentation caused it to be abandoned in most places. Soon after the repeal of Prohibition, the U.S. Federal Bureau of Narcotics (now the Drug Enforcement Administration) began a campaign to portray marijuana as a powerful, addicting substance that would lead users into narcotics addiction. In the 1950s, use of marijuana increased again, along with that of amphetamines and tranquilizers. The social upheaval of the 1960s brought with it a dramatic increase in drug use and some increased social acceptance; by the early 1970s some states and localities had decriminalized marijuana and lowered drinking ages. The 1980s brought a decline in the use of most drugs, but cocaine and crack use soared. The military became involved in border patrols for the first time, and troops invaded Panama and brought its de facto leader, Manuel Noriega, to trial for drug trafficking.

Throughout the years, the public's perception of the dangers of specific substances changed. The surgeon general's warning label on tobacco packaging gradually made people aware of the addictive nature of nicotine. By 1995, the Food and Drug Administration was considering its regulation. The recognition of fetal alcohol syndrome brought warning labels to alcohol products. The addictive nature of prescription drugs such as diazepam (Valium) became known, and caffeine came under scrutiny as well.

Drug laws have tried to keep up with the changing perceptions and real dangers of substance abuse. By 1970 over 55 federal drug laws and countless state laws specified a variety of punitive measures, including life imprisonment and even the death penalty. To clarify the situation, the Comprehensive Drug Abuse Prevention and Control Act of 1970 repealed, replaced, or updated all previous federal laws concerned with narcotics and all other dangerous drugs. While possession was made illegal, the severest penalties were reserved for illicit distribution and manufacture of drugs. The act dealt with prevention and treatment of drug abuse as well as control of drug traffic. The Anti-Drug Abuse Acts of 1986 and 1988 increased funding for treatment and rehabilitation; the 1988 act created the Office of National Drug Control Policy. Its director, often referred to as the drug "czar," is responsible for coordinating national drug control policy.

Corticosteroids, as well as adrenocorticotropic hormone (ACTH), the pituitary gland substance that stimulates the adrenal cortex, have modifying effects on many diseases. Some corticosteroid derivatives mimic the action of the naturally occurring steroid hormone aldosterone, causing increased sodium retention and potassium excretion. Others have the same effects as the naturally occurring steroids cortisone and cortisol, which are classed as glucocorticoids; these affect carbohydrate and fat metabolism, reduce tissue inflammation, and suppress the body's immune defense mechanisms. Cortisone and hydrocortisone are used to treat Addison's disease, a disorder caused by underproduction of the adrenal cortex hormones. These and synthetic steroids are used extensively to treat arthritis and other rheumatoid diseases, including rheumatic heart disease. They are also used in some cases of autoimmune diseases such as systemic lupus erythematosus, in severe allergic conditions such as asthma, in allergic and inflammatory eye disorders, and in some respiratory diseases. The anti-inflammatory, itch-suppressing, and vasoconstrictive properties of steroids make them useful when applied to the skin to relieve diseases such as eczema and psoriasis and insect bites.

Because corticosteroids lower the resistance to infection, patients on steroid therapy cannot be vaccinated for smallpox or immunized. The administration of corticosteroids also causes underproduction of the natural hormones by the adrenal cortex, and so ACTH or corticosteroid therapy must always be withdrawn gradually. In addition, when used in large doses for long periods of time, the drugs can cause atrophy of the adrenal cortex. Side effects of steroid therapy include glaucoma, excess hair growth, and imbalance of many substances, including calcium, nitrogen, potassium, and sodium. Many of the synthetic corticosteroids, such as prednisone, prednisolone, triamcinolone, and betamethasone, are more potent than the naturally occurring compounds.

Antivirals are now available for a wide variety of viral diseases. Ribavirin, available since the mid-1980s, is used to treat respiratory syncytial virus (RSV), a cause of severe childhood respiratory infections. It is thought to inhibit messenger RNA. Ribavirin has few side effects, but is prohibitively expensive for all but the most serious cases. Amantadine and rimantadine, which are effective against strains of influenza A, act by interfering with viral uncoating.

Herpes simplex virus can now be treated by a highly selective drug, acyclovir (Zovirax), that interferes with an enzyme critical to the growth of the DNA chain. Although not a cure, the drug lessens the frequency and severity of outbreaks. Acyclovir is also used to lessen the pain and speed the healing of herpes zoster (shingles).

The search for cures and palliatives for AIDS has yielded drugs such as zidovudine (AZT), which inhibits the transcription of RNA to DNA in human immunodeficiency virus (HIV). Ganciclovir and cidofovir are used in the treatment of cytomegalovirus (CMV), a virus that affects the eyes of immunosuppressed patients. Fomivirsen, which is an antisense drug, is also used to treat CMV.

See also nucleic acid, virus, retrovirus.

Antianxiety drugs frequently prescribed in the United States include the benzodiazepines alprazolam (Xanax) and clonazepam (Clonopin), most often prescribed for panic attacks and general anxiety. Long-term use is discouraged because of side effects (impaired alertness, sedation, interactions with alcohol and other drugs), potential for addiction, and withdrawal symptoms. Nonbenzodiazepine drugs that work by acting on benzodiazepine receptors include zolpidem (Ambien), which is widely prescribed as a sleeping pill. Beta-blockers, usually prescribed for hypertension, are sometimes used for people facing an anxiety-producing "crisis," such as performing on the stage or giving a speech. Buspirone (BuSpar), a drug chemically unrelated to the benzodiazepines or beta-blockers, is often preferred for cases of long-term anxiety because it has fewer side effects, less addictive potential, and no withdrawal symptoms.

Common term for sulfonamide drug, any member of a class of synthetic antibacterial drugs with a particular chemical structure including both sulfur and nitrogen atoms. Their effectiveness against bacteria was discovered in 1932 by Gerhard Domagk, and they became the first chemical substances systematically used against human bacterial infections. Sulfa drugs inhibit the growth and multiplication of certain bacteria (but do not kill them) by interfering with the synthesis of folic acid. Because of their toxicity and growing bacterial resistance, sulfa drugs are no longer in common use (except for urinary-tract infections, certain forms of malaria, and preventing infection of burns), having been largely superseded by less toxic antibiotics.

Learn more about sulfa drug with a free trial on Britannica.com.

Harmful effects of drugs, from overdose or sensitivity to regular doses. Many medicines are dangerous; the margin between dose and overdose is often narrow. A normally safe dose may be toxic in some people, over time, or in combination with certain foods, alcohol, or other drugs. Safeguards to prevent drug poisoning include testing in animals, then human volunteers, and then patients. Drugs unsafe for self-medication are available only to doctors or by prescription. Pharmacists advise the public on proper use.

Learn more about drug poisoning with a free trial on Britannica.com.

Physical and/or psychological dependency on a psychoactive (mind-altering) substance (e.g., alcohol, narcotics, nicotine), defined as continued use despite knowing that the substance causes harm. Physical dependency results when the body builds up a tolerance to a drug, needing increasing doses to achieve the desired effects and to prevent withdrawal symptoms. Psychological dependency may have more to do with one's psychological makeup; some people may have a genetic tendency to addiction. The most common addictions are to alcohol (see alcoholism), barbiturates, tranquilizers, and amphetamines, as well as to the stimulants nicotine and caffeine. Initial treatment (detoxification) should be conducted with medical supervision. Individual and group psychotherapy are critical elements. Alcoholics Anonymous and similar support groups can increase the success rate of other efforts. The ability to admit addiction and the will to change are necessary first steps.

Learn more about drug addiction with a free trial on Britannica.com.

Any chemical agent that affects the function of living things. Some, including antibiotics, stimulants, tranquilizers, antidepressants, analgesics, narcotics, and hormones, have generalized effects. Others, including laxatives, heart stimulants, anticoagulants, diuretics, and antihistamines, act on specific systems. Vaccines are sometimes considered drugs. Drugs may protect against attacking organisms (by killing them, stopping them from reproducing, or blocking their effects on the host), substitute for a missing or defective substance in the body, or interrupt an abnormal process. A drug must bind with receptors in or on cells and cannot work if the receptors are absent or its configuration does not fit theirs. Drugs may be given by mouth, by injection, by inhalation, rectally, or through the skin. The oldest existing catalogue of drugs is a stone tablet from ancient Babylonia (circa 1700 BC); the modern drug era began when antibiotics were discovered in 1928. Synthetic versions of natural drugs led to design of drugs based on chemical structure. Drugs must be not only effective but safe; side effects can range from minor to dangerous (see drug poisoning). Many illegal drugs also have medical uses (see cocaine; heroin; drug addiction). Seealso drug resistance; pharmacology; pharmacy.

Learn more about drug with a free trial on Britannica.com.

Synthetic version of a controlled narcotic substance. Designer drugs usually are synthesized for the first time in an attempt to create a chemical whose molecular structure differs only slightly from that of some well-known controlled substance but whose effects are essentially the same. Because of the difference in molecular structure, the designer drug, unlike the controlled substance, ordinarily will not be specifically listed as illicit by law-enforcement organizations. Many designer drugs are manufactured in clandestine laboratories, often by amateurs; for this reason they are sometimes more dangerous than the drugs they are intended to replace. One of the best-known is MDMA (3,4- methylenedioxymethamphetamine), a variation of methamphetamine, popularly called Ecstasy. Nonnarcotic synthetic chemical compounds designed to interact with specific proteins and enzymes in order to combat disease also have been called designer drugs.

Learn more about designer drug with a free trial on Britannica.com.

Any drug used to treat depression. The three main types inhibit the metabolism of serotonin and norepinephrine in the brain. The aim is to keep these monoamine neurotransmitters from dropping to levels associated with depression. The drugs may take a few weeks to show any effect. Tricyclic antidepressants, which inhibit inactivation of norepinephrine and serotonin, help more than 70percnt of patients. Monoamine oxidase (MAO) inhibitors apparently block the action of MAO, an enzyme that helps break down norepinephrine, serotonin, and dopamine in neurons. They have unpredictable side effects and are usually given only when tricyclic drugs do not help. Selective serotonin reuptake inhibitors (SSRIs) apparently block reabsorption only of serotonin, allowing its levels to build up in the brain. SSRIs, which include fluoxetine (trade name Prozac), often help with depression unrelieved by tricyclics or MAO inhibitors and have milder side effects.

Learn more about antidepressant with a free trial on Britannica.com.

Agency of the U.S. Department of Health and Human Services. Established in 1927, it inspects, tests, approves, and sets safety standards for foods and food additives, drugs, chemicals, cosmetics, and household and medical devices. It can prevent untested products from being sold and take legal action to halt the sale of undoubtedly harmful products or of products that involve a health or safety risk. Its authority is limited to interstate commerce; it cannot control prices nor directly regulate advertising except of prescription drugs and medical devices.

Learn more about Food and Drug Administration (FDA) with a free trial on Britannica.com.