Digitalis (redirected from Digitalis glycosides)

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 B.C.; 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

Drug derived from leaves of the common foxglove and used as a drug that strengthens heart muscle contraction. It was first prescribed in the 18th century. Its active principles belong to a class of steroids called cardiac glycosides. Their dosage must be carefully monitored because the lethal dose may be only three times the effective dose. Digitoxin and digoxin are among the most commonly prescribed forms of digitalis.

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digitalis

1. any Eurasian scrophulariaceous plant of the genus Digitalis, such as the foxglove, having bell-shaped flowers and a basal rosette of leaves

2. 

a. a drug prepared from the dried leaves or seeds of the foxglove: a mixture of glycosides used medicinally to treat heart failure and some abnormal heart rhythms

b. any cardiac glycoside, whatever its origin

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digitalis [dij·ə′tal·əs]

(pharmacology)

The dried leaf of the purple foxglove plant (Digitalis purpurea), containing digitoxin and gitoxin; constitutes a powerful cardiac stimulant and diuretic.

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Digitalis [dij·ə′tal·əs]

(botany)

A genus of herbs in the figwort family, Scrophulariaceae.

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Digitalis 

a genus of plants of the family Scrophulariaceae. Plants of this genus are perennial or biennial grasses; rarely are they subshrubs or shrubs. The alternate, entire leaves are lanceolate or oblong. The yellow, purple, or yellow-brown flowers are irregular and often large; they are generally in dense terminal racemes. The perianth is five-parted; the bilabiate corolla is campanulate, thimble-shaped, or inflated. The fruit is a capsule.

There are approximately 35 species of Digitalis, distributed in Europe, western Asia and northern Africa; the Mediterranean region abounds in Digitalis. Of the six species found in the USSR, four grow only in the Caucasus and two grow in the Caucasus, the European USSR, and Western Siberia. They are found primarily in hardwood and mixed forests and in meadows, thickets, and pastures; they also grow on slopes.

All species of Digitalis are poisonous because they contain glycosides, primarily in their leaves. Some species are valuable medicinal herbs. These species include common foxglove (Digitalis purpurea) and yellow foxglove (D. grandiflora), which grow in the European USSR, the Caucasus, and the southern part of Western Siberia; Grecian foxglove (D. lanata), which grows in the Transcarpathian and Odessa oblasts; and such Caucasian species as rusty foxglove (D. ferruginea), D. Schischkinii, and D. ciliata.

The glycosides in the leaves regulate heart activity, increase urine elimination, and reduce edema. Medicinal preparations in the form of powders, tinctures, extracts, and neogalenic preparations (such as gitalen) are made from dried leaves, as are secondary glycosides (digitoxin, digoxin). Digitalis preparations are used under strict medical supervision for treating heart disease. Some species of Digitalis are ornamentals.

In the USSR, common foxglove is cultivated in Krasnodar Krai and Western Siberia; Grecian foxglove is raised in the Northern Caucasus and the Ukraine. Good yields are obtained on light chernozem soils. Foxglove should be planted on fields that have lain fallow or on which winter crops, annual hay grasses, and well-fertilized industrial and other row crops were previously cultivated. The seeds are generally sown 60 cm apart in the fall or spring; the sowing rate is 6–7 kg of seeds per hectare. Organic and inorganic fertilizers are applied during plowing. In the first and second years, the plants require nitrogen and phosphorous supplements.

Under optimum weather conditions and agricultural methods, the leaves may be gathered two or three times in the first year and one or two times in the second. The leaves of annual crops may be harvested first in July or August and later at intervals of one to 1 ^x/i months. The leaves of biennial foxglove may first be picked between shoot formation and flowering and later during massive flowering.

REFERENCES

Naperstianka. Moscow, 1954.
Atlas lekarstvennykh rastenii SSSR. Moscow, 1962.
Lekarstvennye rasteniia SSSR kul’tiviruemye i dikorastushchie. Edited by A. A Khotin [et al.]. Moscow, 1967.

T. V. EGOROVA