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Digitalis

Digitalis

Doctors often treat illnesses with drugs derived (obtained) from special substances found in plants. One of the most important of these drugs is digitalis, which is used to treat congestive heart failure. This heart condition occurs when the heart becomes enlarged and loses some of its effectiveness in pumping blood. Swelling caused by an accumulation of fluid in the arms and legs or hands and feet may be a sign of congestive heart failure. As long ago as the thirteenth century, people who used "folk" remedies began to notice that a plant commonly known as foxglove produced a medicine that could be used to treat some types of this swelling, called "dropsy." The medical term for swelling caused by a buildup of fluid is edema. Digitalis is one of the most useful drugs in treating heart disease. It works by making the heart's contractions stronger without causing it to beat faster and become overworked. This results in a slower, more effective heartbeat with longer periods of rest for the heart in between.

Foxglove

Common foxglove is grown in gardens as a popular flower and also grows wild along roadsides and in meadows or logged areas, mainly in the western United States. The botanical name for common foxglove is Digitalis purpurea. Foxglove was brought to the United States by European migrants centuries ago. The plant has tube-shaped, spotted, purple flowers and grows to about five feet tall, with many large, thick, hairy leaves at the base of a tall stem. The variety grown in gardens varies in color from white to a deep rose.

Digitalis is one of the most well known medicines derived from a plant. Today scientists are searching in jungles and tropical rain forests for other plants that may contain substances to cure cancer, hepatitis, AIDS, and other serious diseases. Native medicine healers have used plants to treat illnesses among their people for thousands of years, and scientists today are working with modern-day medicine men in hopes of finding new wonder drugs among the earth's fast-disappearing natural resources.

The Pharmacy in the Garden

Other drugs used today that come from plants include tubocurarine, a surgical anesthetic derived from the curare vine; ephedrine, the active ingredient in decongestants, found in the stem of a Chinese shrub called mahuang; the opium poppy, which contains more than 20 alkaloids, of which morphine, codeine, and heroin are the most well known; aspirin, a painkiller derived from willow tree bark; reserpine, an anti-hypertensive that comes from the snakeroot plant; atropine, an intestinal (smooth muscle) antispasmodic and pupil dilator found in belladonna (deadly nightshade); and physostigmine, a glaucoma treatment and atropine poisoning antidote (remedy) derived from the Calabar bean.

Withering's Studies

In 1775 an English doctor named William Withering (1741-1799) began studying the foxglove plant. He learned that an effective medicine for treating heart ailments could be made from drying leaves picked just before the plant blossomed and crushing them into a powder. Withering also discovered that this medicine, digitalisone of a number of substances called found in the plantcould be poisonous if the patient was given too much. Withering was aware that digitalis was effective only in certain forms of dropsy (edema), but apparently did not associate this with the cardiac actions of the drug. Withering published his findings about digitalis in 1785, but in spite of his warnings about proper dosage, many doctors prescribed the medicine in doses that were too large and for sicknesses it could not cure.

The active principles of digitalis were not known to researchers until the mid-1800s, when two French scientists, Homolle Ouevenne and Theodore Ouevenne, found the substance digitalin in the foxglove plant. In 1875 Oscar Schmiedeberg (1838-1921) identified the potent chemical digitoxin in the plant, and in 1930 the English chemist Sydney Smith obtained the medicine used today, digoxin, from the wooly foxglove plant, Digitalis lanata.

Today doctors know that if too much digitalis enters the circulatory system the patient may experience nausea, vomiting, trouble with vision (seeing too much yellow or green), and a very slow and irregular heartbeat. A larger amount of digitalis can result in convulsions (severe seizures) and death. Even grazing animals that eat too much of the foxglove plant can become poisoned by its glycosides.

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digitalis

digitalis (dĬj´Ĭtăl´Ĭs), 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 BC; it was later obtained from the foxglove plant, Digitalis purpurea, and from fuchsia (see figwort). It was used in the 19th cent. to treat dropsy (edema). Digitalislike substances are found in a wide variety of plants and animals, including the poisons of some toad species. Foxglove remains the main source for the drug used medically today.

Chemically, digitalis is composed of a sugar (glycoside), a steroid, and a cyclic ester known as a lactone; the pharmacological activity varies according to differences, occurring naturally or introduced synthetically, in the steroid or sugar portions. Common preparations include digitalis, digitoxin, and digoxin, all from foxglove, and ouabain from Strophanthus gratus, the ouabaio tree; these vary both in solubility and in rapidity and duration of effect.

Digitalis slows the pulse and slows the conduction of nerve impulses in the heart. By increasing the amount of calcium available to the heart muscle, it improves the force of each heartbeat and increases the amount of blood pumped. It is used in the treatment of congestive heart failure and cardiac arrhythmias. The mechanism by which it acts to enhance heart muscle contraction is not definitely known. Toxic effects include nausea, vomiting, and visual disturbances.

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digitalis

digitalis A preparation of the dried leaves or seeds of the foxglove (Digitalis), used historically as a heart stimulant. Modern clinically prescribed drugs derived from digitalis include digoxin and digitoxin, both of which belong to a class of drugs known as the cardiac glycosides. They are used to treat heart failure and some forms of arrhythmia because of their ability to increase the force of contraction of the heart muscle. Their toxic effects arise from their capacity to disturb the normal rhythm of the heart.

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Digitalis

Digitalis (foxgloves; family Scrophulariaceae) A genus of tall herbs that have alternate leaves and attractive, drooping, 2-lipped, bell-like flowers. They are cultivated for their flowers and for the alkaloid digitalis, used for heart stimulation. There are about 20 species, found in Europe and Central Asia.

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digitalis

digitalis plant of the foxglove family XVII; drug prepared from this XVIII. — modL., sb. use of L. digitālis pert. to the finger, after the G. name of the foxglove, fingerhut ‘finger-hat’, thimble.

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digitalis

dig·i·tal·is / ˌdijiˈtalis/ • n. a drug prepared from the dried leaves of foxglove and containing substances (notably digoxin and digitoxin) that stimulate the heart muscle.

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digitalis

digitalis (dij-i-tay-lis) n. an extract from the dried leaves of foxgloves (Digitalis species), which contains various substances, including digitoxin and digoxin, that stimulate heart muscle.

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digitalis

digitalis Drug obtained from the leaves of the foxglove (Digitalis purpurea), used to treat heart disease. It increases heart contractions and slows the heartbeat.

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digitalis

digitalis An alkaloid that is used for heart stimulation; it is derived from fox-gloves (Digitalis). See CARDIAC GLYCOSIDE.

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digitalis

digitalisAlice, chalice, challis, malice, palace, Tallis •aurora australis •Ellis, trellis •necklace •aurora borealis, Baylis, digitalis, Fidelis, rayless •ageless • aimless • keyless •amaryllis, cilice, Dilys, fillis, Phyllis •ribless • lidless • rimless •kinless, sinless, winless •lipless • witless • annus mirabilis •annus horribilis • syphilis •eyeless, skyless, tieless •polis, solace, Wallace •joyless •Dulles, portcullis •accomplice •Annapolis, Indianapolis, Minneapolis •Persepolis •acropolis, cosmopolis, Heliopolis, megalopolis, metropolis, necropolis •chrysalis • surplice • amice • premise •airmiss • Amis • in extremis • Artemis •promise •pomace, pumice •Salamis •dermis, epidermis, kermis

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Digitalis

Digitalis

How digitalis is used

Risks and side effects

Resources

Digitalis is a drug that has been used for centuries to treat heart disease. The active ingredient in the drug is glycoside, a chemical compound that contains a sugar molecule linked to another molecule. The glycoside compound can be broken down into a sugar and nonsugar compound. Though current digitalis drugs are synthetic, that is, artificially made, early forms of the drug were derived from a plant.

Digitalis is a derivative of the plant Digitalis purpurea, or purple foxglove. The plants name, Digitalis (from the Latin digit, finger) describes the finger-shaped purple flowers it bears. English physician William Withering (17411799), who experimented with the extract in fowls and humans, first observed the effects of the plant extract on the heart in the late eighteenth century.

Witherings keen interest in botany led him to collect plant specimens, as did his love for one of his patients (whom he married), a flower painter. Withering noted that old country women used foxglove to treat dropsy (edema), an accumulation of fluids caused by a failing heart. Willing to consider these old wivestales, Withering embarked on a detailed study of digitalis. He determined the most effective treatment forma powder made from dried leaves picked just before the plant blossomedand, of critical importance, the correct dosage for different cardiac conditions. Equally important, Withering established clear standards for when to discontinue administration of the drug, which can be toxic when used in excessive amounts.

Withering reported his results in a treatise entitled, The Foxglove and an Account of its Medical Properties, with Practical Remarks on Dropsy. His explanations of the effects of foxglove on the heart have not stood up to the test of time, but his prediction that it could be converted to salutary ends certainly has. Indeed, digitalis remains the oldest drug in use for the treatment of heart disease, as well as the most widespread, in use today.

The active principles of digitalis eluded researchers until the mid-1800s. French scientists Augustin Homolle and Theódore Ouevenne won a cash prize in 1844 from the Societe de Pharmacie in Paris (France) when they isolated digitalin. Oscar Schmiedeberg (18381921) isolated the highly potent digitoxin in 1875. English chemist Sydney Smith obtained digoxin from woolly foxglove (Digitalis lanata ) in 1930.

The digitalis drugs come in many forms, differing in their chemical structure. As a group, they are classified as cardiac inotropes. Cardiac, of course, refers to the heart. An inotrope is a substance that has a direct effect on muscle contraction. Positive inotropism is an increase in the speed and strength of muscle contraction, while negative inotropism is the opposite. Digitalis has a positive inotropic effect on the heart muscle.

How digitalis is used

Digitalis is used to bolster the ailing heart in congestive heart failure. In this condition, the heart muscle has stretched while straining to pump blood against a back pressure. The back pressure may be caused by high blood pressure, or it may be the result of a leak caused by a faulty aortic valve or a hole in the wall (septum) dividing the right and left halves of the heart. When these conditions occur, the heart muscle, or myocardium, must exert greater and greater pressure to force blood through the body against the resistant force. Over time, the strain will stretch the heart muscle, and the size of the heart increases. As the heart muscle changes in these ways, its pumping action becomes less and less effective. Congestive heart failure occurs when the myocardium has been stretched too far. At this juncture the patient must have a heart transplant or he/she will die.

The administration of digitalis, however, can forestall the critical stage of the disease. Digitalis has a direct and immediate effect on the myocardium. By a mechanism not well understood, digitalis increases the levels of intracellular calcium, which plays an important role in the contraction of the muscles. Almost as soon as the drug has been administered, the heart muscle begins to contract faster and with greater force. As a result, its pumping efficiency increases and the supply of blood to the body is enhanced. Digitalis also tends to bring about a decrease in the size of the ventricles of the failing heart as well as a reduction in wall tension.

In addition to its immediate effect on the heart muscle, the drug affects the autonomic nervous system, slowing the electrical signal that drives the heartbeat. As heart contractions become more efficient, the heart rate slows. For this reason, the drug is said to have a negative chronotropic effect (the prefix chrono refers to time).

As digitalis stabilizes the myocardium, appropriate steps can also be taken to correct the original cause of the disease, if possible. The patients blood pressure can be lowered with medications, or heart surgery can be performed to replace a faulty valve or patch a hole in the septum. When it is not possible to improve cardiac function by other means, the patient can be maintained on digitalis for many years.

Risks and side effects

The effect of digitalis is dose related. The higher the dose, then the more pronounced the cardiac reaction. The immediate and direct effect of the drug dictates that the physician closely monitor the patient and adjust the digitalis dosage as needed to provide the corrective effect. At the same time, the physician should be careful not to institute a toxic reaction. Digitalis is a very potent and active drug and can quickly create an overdose situation if the patient is not closely watched. In the case of an overdose, the patients heart will begin to beat out of rhythm (arrhythmia) and very rapidly (tachycardia). In addition, the drug may affect the nervous system and cause headaches, vision problems such as blurring and light sensitivity, and sometimes convulsions.

Withering already recognized the toxicity of digitalis and warned against the careless administration of the drug in too high a dose. Despite Witherings warnings, physicians in the early nineteenth century often overdosed their patients. Consequently, the drug was

KEY TERMS

Aortic valve The one-way valve that allows blood to pass from the hearts main pumping chamber, the left ventricle, into the bodys main artery, the aorta.

Cardiologist A physician who specializes in the diagnosis and treatment of heart disease.

Myocardium The heart muscle.

Oxygenation The process, taking place in the lungs, by which oxygen enters the blood to be transported to body tissues.

Septum The wall that divides the right side of the heart (which contains used blood that has been returned from the body) from the left side of the heart (which contains newly oxygenated blood to be pumped to the body).

considered too dangerous for the greater part of the nineteenth century and was used little. Later in the same century, however, the beneficial properties of digitalis were reassessed, and the drug became an essential element in the cardiologists pharmacopeia.

Other drugs to treat diseases have been developed over time, of course, but none has replaced digitalis as the standard therapy for heart failure. A drug of ancient lineage, digitalis remains one of the most reliable and most used medicines.

Resources

BOOKS

Beers, Mark H., et al., eds. The Merck Manual of Diagnosis and Therapy. Whitehouse Station, NJ: Merck Research Laboratories, 2006.

The Complete Drug Reference: Micromedex, Thomson Healthcare and U.S. Pharmacopeia. Yonkers, NY: Consumer Reports Books, 2001.

Larson, Litin, Scott C., ed. Mayo Clinic Family Health Book. New York: HarperResource, 2003.

Larry Blaser

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Digitalis

Digitalis

Digitalis is a drug that has been used for centuries to treat heart disease . The active ingredient in the drug is glycoside, a chemical compound that contains a sugar molecule linked to another molecule. The glycoside compound can be broken down into a sugar and nonsugar compound. Though current digitalis drugs are synthetic, that is, man-made, early forms of the drug were derived from a plant .

Digitalis is a derivative of the plant Digitalis purpurea, or purple foxglove. The plant's name, Digitalis (from the Latin digit, finger) describes the finger-shaped purple flowers it bears. The effects of the plant extract on the heart were first observed in the late eighteenth century by William Withering, who experimented with the extract in fowls and humans. Withering reported his results in a treatise entitled, "The Foxglove and an Account of its Medical Properties, with Practical Remarks on Dropsy." His explanations of the effects of foxglove on the heart have not stood up to the test of time, but his prediction that it could be "converted to salutary ends" certainly has. Indeed, digitalis remains the oldest drug in use for the treatment of heart disease, as well as the most widespread, in use today.

The digitalis drugs come in many forms, differing in their chemical structure. As a group they are classified as cardiac inotropes. Cardiac, of course, refers to the heart. An inotrope is a substance that has a direct effect on muscle contraction. Positive inotropism is an increase in the speed and strength of muscle contraction, while negative inotropism is the opposite. Digitalis has a positive inotropic effect on the heart muscle.


How digitalis is used

Digitalis is used to bolster the ailing heart in congestive heart failure. In this condition, the heart muscle has stretched while straining to pump blood against a back pressure . The back pressure may be caused by high blood pressure, or it may be the result of a leak caused by a faulty aortic valve or a hole in the wall (septum) dividing the right and left halves of the heart. When these conditions occur, the heart muscle, or myocardium, must exert greater and greater pressure to force blood through the body against the resistant force. Over time the strain will stretch the heart muscle, and the size of the heart increases. As the heart muscle changes in these ways, its pumping action becomes less and less effective. Congestive heart failure occurs when the myocardium has been stretched too far. At this juncture the patient must have a heart transplant or he will die.

The administration of digitalis, however, can forestall the critical stage of the disease. Digitalis has a direct and immediate effect on the myocardium. By a mechanism not well understood, digitalis increases the levels of intracellular calcium , which plays an important role in the contraction of the muscles. Almost as soon as the drug has been administered, the heart muscle begins to contract faster and with greater force. As a result, its pumping efficiency increases and the supply of blood to the body is enhanced. Digitalis also tends to bring about a decrease in the size of the ventricles of the failing heart as well as a reduction in wall tension.

In addition to its immediate effect on the heart muscle, the drug affects the autonomic nervous system , slowing the electrical signal that drives the heartbeat. As heart contractions become more efficient, the heart rate slows. For this reason, the drug is said to have a negative chronotropic effect (the prefix chrono- refers to time).

As digitalis stabilizes the myocardium, appropriate steps can also be taken to correct the original cause of the disease, if possible. The patient's blood pressure can be lowered with medications, or heart surgery can be performed to replace a faulty valve or patch a hole in the septum. When it is not possible to improve cardiac function by other means, the patient can be maintained on digitalis for many years.


Risks and side effects

The effect of digitalis is dose related. The higher the dose, the more pronounced the cardiac reaction. It is this immediate and direct effect of the drug that dictates that the physician closely monitor his patient and adjust the digitalis dosage as needed to provide the corrective effect, while being careful not to institute a toxic reaction. Digitalis is a very potent and active drug and can quickly create an overdose situation if the patient is not closely watched. In the case of an overdose, the patient's heart will begin to beat out of rhythm (arrhythmia) and very rapidly (tachycardia). In addition, the drug may affect the nervous system and cause headaches, vision problems such as blurring and light sensitivity, and sometimes convulsions.

Withering already recognized the toxicity of digitalis and warned against the careless administration of the drug in too high a dose. Despite Withering's warnings, physicians in the early nineteenth century often overdosed their patients. As a consequence, the drug was considered too dangerous for the greater part of the nineteenth century and was used little. Later in the same century, however, the beneficial properties of digitalis were reassessed, and the drug became an essential element in the cardiologist's pharmacopeia.

Other drugs to treat diseases have been developed over time, of course, but none has replaced digitalis as the standard therapy for heart failure. A drug of ancient lineage, digitalis remains one of the most reliable and most used medicines.

Resources

books

The Complete Drug Reference: United States Pharmacopeia. Yonkers, NY: Consumer Reports Books, 1992.

Larson, David E., ed. Mayo Clinic Family Health Book. New York: William Morrow, 1996.


Larry Blaser

KEY TERMS

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Aortic valve

—The one-way valve that allows blood to pass from the heart's main pumping chamber, the left ventricle, into the body's main artery, the aorta.

Cardiologist

—A physician who specializes in the diagnosis and treatment of heart disease.

Myocardium

—The heart muscle.

Oxygenation

—The process, taking place in the lungs, by which oxygen enters the blood to be transported to body tissues.

Septum

—The wall that divides the right side of the heart (which contains "used" blood that has been returned from the body) from the left side of the heart (which contains newly oxygenated blood to be pumped to the body).

Cite this article
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"Digitalis." The Gale Encyclopedia of Science. . Encyclopedia.com. 11 Sep. 2018 <http://www.encyclopedia.com>.

"Digitalis." The Gale Encyclopedia of Science. . Encyclopedia.com. (September 11, 2018). http://www.encyclopedia.com/science/encyclopedias-almanacs-transcripts-and-maps/digitalis-0

"Digitalis." The Gale Encyclopedia of Science. . Retrieved September 11, 2018 from Encyclopedia.com: http://www.encyclopedia.com/science/encyclopedias-almanacs-transcripts-and-maps/digitalis-0

Learn more about citation styles

Citation styles

Encyclopedia.com gives you the ability to cite reference entries and articles according to common styles from the Modern Language Association (MLA), The Chicago Manual of Style, and the American Psychological Association (APA).

Within the “Cite this article” tool, pick a style to see how all available information looks when formatted according to that style. Then, copy and paste the text into your bibliography or works cited list.

Because each style has its own formatting nuances that evolve over time and not all information is available for every reference entry or article, Encyclopedia.com cannot guarantee each citation it generates. Therefore, it’s best to use Encyclopedia.com citations as a starting point before checking the style against your school or publication’s requirements and the most-recent information available at these sites:

Modern Language Association

http://www.mla.org/style

The Chicago Manual of Style

http://www.chicagomanualofstyle.org/tools_citationguide.html

American Psychological Association

http://apastyle.apa.org/

Notes:
  • Most online reference entries and articles do not have page numbers. Therefore, that information is unavailable for most Encyclopedia.com content. However, the date of retrieval is often important. Refer to each style’s convention regarding the best way to format page numbers and retrieval dates.
  • In addition to the MLA, Chicago, and APA styles, your school, university, publication, or institution may have its own requirements for citations. Therefore, be sure to refer to those guidelines when editing your bibliography or works cited list.