Also found in: Dictionary, Thesaurus, Medical, Legal, Acronyms, Idioms, Wikipedia.


substances used in medicine either externally or internally for curing, alleviating, or preventing a disease or deficiency. At the turn of the century only a few medically effective substances were widely used scientifically, among them etherether,
any of a number of organic compounds whose molecules contain two hydrocarbon groups joined by single bonds to an oxygen atom. The most common of these compounds is ethyl ether, CH3CH2OCH2CH3
..... Click the link for more information.
, morphinemorphine,
principal derivative of opium, which is the juice in the unripe seed pods of the opium poppy, Papaver somniferum. It was first isolated from opium in 1803 by the German pharmacist F. W. A. Sertürner, who named it after Morpheus, the god of dreams.
..... Click the link for more information.
, digitalisdigitalis
, any of several chemically similar drugs used primarily to increase the force and rate of heart contractions, especially in damaged heart muscle. The effects of the drug were known as early as 1500 B.C.
..... Click the link for more information.
, diphtheria antitoxin, smallpox vaccine, ironiron,
metallic chemical element; symbol Fe [Lat. ferrum]; at. no. 26; at. wt. 55.845; m.p. about 1,535°C;; b.p. about 2,750°C;; sp. gr. 7.87 at 20°C;; valence +2, +3, +4, or +6. Iron is biologically significant.
..... Click the link for more information.
, quininequinine
, white crystalline alkaloid with a bitter taste. Before the development of more effective synthetic drugs such as quinacrine, chloroquine, and primaquine, quinine was the specific agent in the treatment of malaria.
..... Click the link for more information.
, iodineiodine
[Gr.,=violet], nonmetallic chemical element; symbol I; at. no. 53; at. wt. 126.90447; m.p. 113.5°C;; b.p. 184.35°C;; sp. gr. 4.93 at 20°C;; valence −1, +1, +3, +5, or +7.
..... Click the link for more information.
, alcohol, and mercurymercury
or quicksilver
[from the Roman god Mercury], metallic chemical element; symbol Hg [Lat. hydrargyrum=liquid silver]; at. no. 80; at. wt. 200.59; m.p. −38.842°C;; b.p. 356.58°C;; sp. gr. 13.55 at 20°C;; valence +1 or +2.
..... Click the link for more information.
. Since then, and particularly since World War II, many important new drugs have been developed, making chemotherapy an important part of medical practice. Such drugs include the antibioticsantibiotic,
any of a variety of substances, usually obtained from microorganisms, that inhibit the growth of or destroy certain other microorganisms. Types of Antibiotics
..... Click the link for more information.
, which act against bacteria and fungi; quinacrine and other synthetics that act against malaria and other parasitic infections; cardiovascular drugs, including beta-blockersbeta-blocker
or beta-adrenergic blocking agent
, drug that reduces the symptoms connected with hypertension, cardiac arrhythmias, angina pectoris, migraine headaches, and other disorders related to the sympathetic nervous system.
..... Click the link for more information.
 and ACE inhibitorsACE inhibitor
or angiotensin-converting enzyme inhibitor
, drug used to reduce elevated blood pressure (see hypertension), to treat congestive heart failure, and to alleviate strain on hearts damaged as a result of a heart attack (see infarction).
..... Click the link for more information.
; diureticsdiuretic
, drug used to increase urine formation and output. Diuretics are prescribed for the treatment of edema (the accumulation of excess fluids in the tissues of the body), which is often the result of underlying disease of the kidneys, liver, lungs, or heart (e.g.
..... Click the link for more information.
, which increase the rate of urine flow; whole blood, plasma, and blood derivatives; anticoagulantsanticoagulant
, any of several substances that inhibit blood clot formation (see blood clotting). Some anticoagulants, such as the coumarin derivatives bishydroxycoumarin (Dicumarol) and warfarin (Coumadin) inhibit synthesis of prothrombin, a clot-forming substance, and other
..... Click the link for more information.
 such as heparinheparin
, anticoagulant produced by cells in many animals. A polysaccharide, heparin is found in the human body and occurs in greatest concentration in the tissues surrounding the capillaries of the lungs and the liver.
..... Click the link for more information.
 and coumarin; various smooth-muscle relaxants such as papaverinepapaverine
, alkaloid found in opium that acts as a muscle relaxant and vasodilator. The drug relaxes the smooth muscle of the larger blood vessels and is used to increase the blood supply to the brain or to the heart, as in the treatment of angina pectoris.
..... Click the link for more information.
, used in heart and vascular diseases; smooth-muscle stimulants; immunologic agents, which protect against many diseases and allergenic substances; hormones such as thyroxinethyroxine
, substance secreted by the thyroid gland. The hormone thyroxine forms by combining the amino acid tyrosine with iodine. Complexed to a protein, it is stored in the follicle stems between thyroid cells.
..... Click the link for more information.
, insulininsulin,
hormone secreted by the β cells of the islets of Langerhans, specific groups of cells in the pancreas. Insufficiency of insulin in the body results in diabetes. Insulin was one of the first products to be manufactured using genetic engineering.
..... Click the link for more information.
, and estrogenestrogen
, any one of a group of hormones synthesized by the reproductive organs and adrenal glands in females and, in lesser quantities, in males. The estrogens cause the thickening of the lining of the uterus and vagina in the early phase of the ovulatory, or menstrual, cycle
..... Click the link for more information.
 and other sex hormones; psychotherapeutics such as antianxiety drugsantianxiety drug,
drug administered for the relief of anxiety. Although their action is not fully understood, most antianxiety medications appear to affect the action of neurotransmitters in the brain (see serotonin and norepinephrine).
..... Click the link for more information.
 and antidepressant drugsantidepressant,
any of a wide range of drugs used to treat psychic depression. They are given to elevate mood, counter suicidal thoughts, and increase the effectiveness of psychotherapy.
..... Click the link for more information.
; cortisonecortisone
, steroid hormone whose main physiological effect is on carbohydrate metabolism. It is synthesized from cholesterol in the outer layer, or cortex, of the adrenal gland under the stimulation of adrenocorticotropic hormone (ACTH).
..... Click the link for more information.
 and synthetic corticosteroid drugscorticosteroid drug
, any one of several synthetic or naturally occurring substances with the general chemical structure of steroids. They are used therapeutically to mimic or augment the effects of the naturally occurring corticosteroids, which are produced in the cortex of the
..... Click the link for more information.
 used in treating inflammatory diseases such as arthritis; vitamins and dietary minerals; antidotes for poisons; and various drugs that act as stimulantsstimulant,
any substance that causes an increase in activity in various parts of the nervous system or directly increases muscle activity. Cerebral, or psychic, stimulants act on the central nervous system and provide a temporary sense of alertness and well-being as well as
..... Click the link for more information.
 or depressantsdepressant,
any one of various substances that diminish functional activity, usually by depressing the nervous system. Barbiturates, sedatives, alcohol, and meprobamate are all depressants. Depressants have various modes of action and effects.
..... Click the link for more information.
 on all or various parts of the nervous system, including analgesicsanalgesic
, any of a diverse group of drugs used to relieve pain. Analgesic drugs include the nonsteroidal anti-inflammatory drugs (NSAIDs) such as the salicylates, acetaminophen, narcotic drugs such as morphine, and synthetic drugs with morphinelike action such as meperidine
..... Click the link for more information.
, narcoticsnarcotic,
any of a number of substances that have a depressant effect on the nervous system. The chief narcotic drugs are opium, its constituents morphine and codeine, and the morphine derivative heroin.

See also drug addiction and drug abuse.
..... Click the link for more information.
, amphetaminesamphetamine
, any one of a group of drugs that are powerful central nervous system stimulants. Amphetamines have stimulating effects opposite to the effects of depressants such as alcohol, narcotics, and barbiturates.
..... Click the link for more information.
, and barbituratesbarbiturate
, any one of a group of drugs that act as depressants on the central nervous system. High doses depress both nerve and muscle activity and inhibit oxygen consumption in the tissues. In low doses barbiturates act as sedatives, i.e.
..... Click the link for more information.
 (see also anesthesiaanesthesia
[Gr.,=insensibility], loss of sensation, especially that of pain, induced by drugs, especially as a means of facilitating safe surgical procedures. Early modern medical anesthesia dates to experiments with nitrous oxide (laughing gas) by Sir Humphry Davy of England
..... Click the link for more information.
; psychopharmacologypsychopharmacology
, in its broadest sense, the study of all pharmacological agents that affect mental and emotional functions. The term is usually applied more specifically to the study and synthesis of drugs used in the control of psychiatric illnesses, namely the
..... Click the link for more information.
; hallucinogenic drughallucinogenic drug
, any of a group of substances that alter consciousness; also called psychotomimetic (i.e., mimicking psychosis), mind-expanding, or psychedelic drug.
..... Click the link for more information.

See also drug resistancedrug resistance,
condition in which infecting bacteria can resist the destructive effects of drugs such as antibiotics and sulfa drugs. Drug resistance has become a serious public health problem, since many disease-causing bacteria are no longer susceptible to previously
..... Click the link for more information.
; drug poisoningdrug poisoning,
toxic effects caused by an administered drug. Worldwide more than 9 million natural and synthetic chemicals have been identified; fewer than 3000 cause more than 95% of acidental and deliberate poisonings.
..... Click the link for more information.
; drug addiction and drug abusedrug addiction and drug abuse,
chronic or habitual use of any chemical substance to alter states of body or mind for other than medically warranted purposes. Traditional definitions of addiction, with their criteria of physical dependence and withdrawal (and often an underlying
..... Click the link for more information.

Sources of Drugs

Drugs are obtained from many sources. Many inorganic materials, such as metals, are chemotherapeutic; hormones, alkaloids, vaccines, and antibiotics come from living organisms; and other drugs are synthetic or semisynthetic. Synthetics are often more effective and less toxic than the naturally obtained substances and are easier to prepare in standardized units. The techniques of genetic engineeringgenetic engineering,
the use of various methods to manipulate the DNA (genetic material) of cells to change hereditary traits or produce biological products. The techniques include the use of hybridomas (hybrids of rapidly multiplying cancer cells and of cells that make a
..... Click the link for more information.
 are being applied to the production of drugs, and genetically engineered livestock that incorporate human genes are being developed for the production of scarce human enzymes and other proteins (see pharmingpharming
, the use of genetically altered livestock, such as cows, goats, pigs, and chickens, to produce medically useful products. In pharming, researchers first create hybrid genes using animal DNA and the human or other gene that makes a desired substance, such as a hormone.
..... Click the link for more information.

Pharmacopoeia and Drug Safeguards

Standards for drugs and tests for their identity, quality, and purity are given in the U.S. pharmacopoeiapharmacopoeia
or pharmocopeia
, authoritative publication designating the properties, action, use, dosage, and standards of strength and purity of drugs. It is compiled under the supervision of professional, usually governmental, authority, and all manufacture and
..... Click the link for more information.
, first published in 1820 and at first revised every 10 years, later every 5 years. The British publish a similar pharmacopoeia. The National Formulary published by the American Pharmaceutical Association gives the composition, description, method of preparation, and dosage for drugs; the Physician's Desk Reference is a privately published compilation of information supplied by drug companies about their drug products, published yearly. The scientific study of drugs, their actions and effects, is pharmacologypharmacology,
study of the changes produced in living animals by chemical substances, especially the actions of drugs, substances used to treat disease. Systematic investigation of the effects of drugs based on animal experimentation and the use of isolated and purified active
..... Click the link for more information.

Legislation to safeguard drug purchasers began in the United States with the Pure Food and Drugs Act of 1906; this was superseded by the more inclusive and more stringent federal Food, Drug, and Cosmetic Act of 1938. Such laws are enforced by the Food and Drug Administration. The 1962 Kefauver-Harris amendments to the Food, Drug, and Cosmetic Act increased the authority of the Food and Drug Administration to regulate testing and marketing of new drugs. There are two marketing classes of drugs: ethical drugs, for which prescriptions are needed, and proprietary drugs, which are sold over the counter without prescription. Many of the latter, such as mouthwashes, gargles, and cold preparations, are only slightly, if at all, effective in curing ailments.


See B. Barber, Drugs and Society (1967); C. B. Clayman, ed., American Medical Association Guide to Prescription and Over-the-Counter Drugs (1988); A. Burger, Drugs and People: Medications, Their History and Origins, and the Way They Act (rev. 1988); United States Pharmacopeial Staff, The Complete Drug Reference (1995).

References in classic literature ?
The doctor stood on the edge, reading formulae every now and then from his black-letter volume, or throwing more drugs and herbs upon the fire, while Wolfert bent anxiously over the pit, watching every stroke of the spade.
Still stupefied by the drug that I had taken, I could lazily wonder what had happened, and I could do no more.
Your master, Poole, is plainly seized with one of those maladies that both torture and deform the sufferer; hence, for aught I know, the alteration of his voice; hence the mask and the avoidance of his friends; hence his eagerness to find this drug, by means of which the poor soul retains some hope of ultimate recovery--God grant that he be not deceived
That is the same drug that I was always bringing him," said Poole; and even as he spoke, the kettle with a startling noise boiled over.
And sometime under the liquor drug, snatches of wisdom came to him far more lucidity than in his sober moments, as, for instance, one night, when he sat on the edge of the bed with one shoe in his hand and meditated on Dede's aphorism to the effect that he could not sleep in more than one bed at a time.
He sold a drug, pretending that it was an antidote to all poisons, and obtained a great name for himself by long-winded puffs and advertisements.
Possibly, but strychnine is a fairly rapid drug in its action.
Then you consider it more likely that the drug was administered in the coffee, but that for some unknown reason its action was delayed.
I believe," continued Lawrence, "that there have been cases where the cumulative effect of a drug, administered for some time, has ended by causing death.
This effort was framed and hung in the drug store window by the side of the ear of corn with an uneven number of rows.
He rushed downstairs and sent somebody--they said the furnace man or somebody in the basement--out to a drug store for some oil and things to bind it up with.
Pediatric Drugs R&D Confronts Several Barriers 9