Derivation

Digitalis is obtained from the leaves of the Digitalis purpurea, or Foxglove. Digitoxin and Digitalin are the two most active principles, but neither will take the place of digitalis in medicinal use.

Medical Properties And Physiological Action

As digitalis irritates mucous membranes which are wanting in tone, it should not be internally given in gastritis, etc. Its action is only manifested on the nerves when toxic doses are administered. Its action is chiefly manifested upon the circulatory system, as it increases the pulse-force and arterial pressure, and size of the pulse-wave, and slows the pulse, when moderate doses are given. When full medicinal doses are employed, or when poisonous doses are injected, the action of the heart becomes very irregular, and dicrotic, and, according to Hare, it is not due to weakness, for the cardiac beats when they occur, are in themselves more forcible than in health. Digitalis only effects respiration when poisonous doses are given, when it is slowed.

The medicinal dose has little or no effect upon the normal temperature of the body ; it has no effect on the kidney structure, but sometimes causes nausea and indigestion by irritating the stomach.

Digitalis is a cardiac stimulant, and not a depressant.

Therapeutic Uses

It is employed in all cardiac diseases, and is beneficial when the heart is irritable and palpitation is present, and the cause is not due to indigestion. It is also employed in cardiac weakness from collapse, and is particularly serviceable in aconite poisoning. To counteract its slow action, it should be preceded by ammonia and alcohol in urgent cases. It is also useful as a diuretic in congested kidney affections, and in cardiac dilatation and asthenia. Tannic acid is the chemical antidote; also the stomach-pump, and emetics if the heart is not affected; external heat about abdomen, and the maintainance of a horizontal position for several days after the active poisonous symptoms are manifested. Tincture of aconite is the physiological antidote. In all cases it is necessary that the slow absorption and elimination of digitalis should be remembered. Hypodermic injections of the tincture m xv-xxx are valuable in sudden heart depression resulting from any cause, such as shock or collapse from hemorrhage, or surgical operations, etc., etc. Digitalis must be used with care in fatty heart, aneurism, and cerebral endocarditis.