<s>[INST] context: Digoxin's primary mechanism of action involves inhibition of the sodium potassium adenosine triphosphatase (Na+/K+ ATPase), mainly in the myocardium. This inhibition causes an increase in intracellular sodium levels, resulting in decreased activity of the sodium-calcium exchanger, which normally impos three extracellular sodium ions into the cell and transpos one intracellular calcium ion out of the cell. The reversal of this exchanger causes an increase in the intracellular calcium concentration that is available to the contractile proteins. Increased intracellular calcium lengthens phase 4 and phase 0 of the cardiac action potential, which leads to a decrease in hea rate. Increased amounts of Ca2+ also leads to increased storage of calcium in the sarcoplasmic reticulum, causing a corresponding increase in the release of calcium during each action potential. This leads to increased contractility (the force of contraction) of the hea without increasing hea energy expenditure Refer kDT 7/e p 212 [/INST] question: Mechanism of action of disgitalis is | options: A: Inhibits Na +K+ ATPase pump B: Inhibits Na+ H+ ATPase pump C: Active metabolite are produced in liver D: Inhibit calcium concentrations in blood | answer: A </s>