<prompt> Which drug inhibits Na-K ATPase pump -DigitalisAmiodaroneVarapamilHydralazine  <response>: Ans. is a i.e., Digitalis o Following figure will help you to understand the mechanism of action of digoxin.o There are two important pumps in myocytes:i 3Nal Ca2 exchanger This pump transports Ca2 in exchange of Na. When Na concentration inside the myocyte is high, NaCa2 exchanger cause efflux of Na out of the myocytes and in exchange it causes influx of Ca2 inside the myocytes. NaVCa2 exchanger does not require ATP to function, ions move along their concentration gradient.ii NaVK ATPase This pump causes efflux of Na in exchange of influx of K.o Digitalis inhibits NaK ATPase. Therefore, efflux of Na by Na K ATPase is inhibited. This results in increased concentration of Na inside the myocytes.o Increased Na concentration causes increased efflux of Na by NaCa2 exchanger with an increased influx of Ca2 inside of myocytes.o Thus, intracellular concentration of Ca2 is increased which results in increased force of cardiac contractiono It is worth noting that Na efflux is affected in two ways:i Na efflux is dcreased by NaK ATPase due to inhibition of NaK ATPase by digoxin.ii Na efflux is increased by Ca2Na exchanger due to increased intracellular Na as a result of decreased Na efflux by NaK ATPase 