Final answer:
Digoxin inhibits the sodium-potassium ATPase pump, increasing intracellular calcium in heart muscles and enhancing contractility, while also increasing vagal tone, lowering heart rate.
Step-by-step explanation:
Digoxin's mechanism of action is the inhibition of the sodium-potassium ATPase pump. In the heart, this inhibition results in an increase in calcium concentrations in myocytes, which subsequently causes an increase in the strength of the contraction, acting as a positive inotropic agent. The drug digitalis, from which digoxin is derived, similarly elevates intracellular calcium levels and boosts contractility. Moreover, digoxin increases vagal tone by enhancing parasympathetic stimulation via the vagus nerve, which contributes to a decrease in heart rate (HR).