Digitalis is the dried leaves of the second year's growth of Foxglove, Digitalis purpurea.

Pharmacodynamics.

Central Nervous System. - Stimulation in the medulla of the cardio-inhibitory (and vasoconstrictor)centers; later, respiratory and vomiting centers, and reflexes to motor tracts.

Muscular system is not affected in mammals.

Respiration is slowed in toxic conditions.

Heart. - Vagus action prolongs diastole, while direct action irritates heart muscle, extending and energizing systole.

Blood-pressure is increased, partly by the increased force of the heart-beat, partly by irritation contraction of the vessel walls, partly by centric vasoconstriction.

Alimentary tract tends to be irritated.

Secretory Glands. - Kidneys manifest increased activity, due in part to local epithelial irritation, and in part to augmented blood-pressure; most evident in cardiac dropsy.

Metabolism. - Effect inappreciable.

Temperature is lowered when fever exists.

Absorption takes place slowly from the alimentary canal.

Excretion. - Probably oxidized in the body.

Local Action. - Digitalis is very irritant to the eye and to mucosa; abscesses have followed when used hypodermically.

Tolerance. - Not acquirable by man.

Symptoms.

Therapeutic Doses.

Slowing and strengthening of heart rhythm.

Toxic Doses.

Uneasiness and giddiness.

Nausea and vomiting.

Great muscular weakness.

Very slow intermittent pulse; or, if cumulative, racing, fluttering pulse with great precordial anxiety.

Mental distress.

Therapeutics.

Digitalis is employed in cardiac incompetency, whether due to simple dilatation or to valvular lesions; and is seemingly a specific in auricular fibrillation.

Dosage.

Fluidextractum Digitalis, 0.05 mil.

Tinctura Digitalis, 0.3 to 1 mil, repeated very cautiously.

Digitalis is slowly absorbed, but its effect is prolonged. A single dose will keep the heart slowed for several days. Therefore, repeated doses are liable to produce a cumulative effect, with severe toxic symptoms.

Crimson = stimulation Green = irritation.