Cardiac glycoside from the leaves of foxglove. It has a blocking effect on the transport sodium / potassium ATP phase, after which the content of sodium ions in cardiomyocytes increases, calcium channels open, calcium enters the cells. An increase in the concentration of sodium accelerates the release of calcium from the sarcoplasmic reticulum and increases its content in the cell, thereby inhibiting the troponin complex, which inhibits the interaction of actin and myosin. The strength and speed of contraction of the cardiac muscle increases regardless of the preliminary stretching of the myocardium - the systole is shortened, becoming energetically economical. Increased myocardial contractility contributes to an increase in the shock volume of the blood.
Reduction of the end systolic and diastolic volumes of the heart together with an increase in myocardial tone reduces the size of the heart, reducing the need for myocardium in oxygen.
Carries out a negative chronotropic action, reduces the increased sympathetic activity, increasing the sensitivity of cardiopulmonary baroreceptors.Strengthening the activity of the vagus nerve, has an antiarrhythmic effect due to the elongation of the refractory period and a decrease in the rate of impulses through the atrioventricular node. The effect is improved by direct action on atrioventricular node and sympatholytic effects.
In patients with excessive stretching of the heart or with normal contractility has a direct vasoconstrictive effect. In patients with chronic heart failure, it produces mediated vasodilating effect, raises diuresis and reduces venous pressure, relieves dyspnea and swelling.
In toxic and sub-toxic doses has a positive butmotropic effect.
The initial effect appears after 1.5-2 hours, reaches a maximum after 4-6 hours.