Digoxin

White powder. Soluble in DMSO (100mM) or methanol. Cardiac glycoside from the leaves of Digitalis lanata. It is used to treat cardiac arrhythmias. It is often used as a model substrate of P-glycoprotein (Pgp) (0.01-10µM) and an inhibitor of Na+/K+-ATPase. Inhibits membrane-bound ?-subunits of the Na+/K+ ATPase pump in myocytes. The primary mechanism of action involves inhibition of the Na+/K+ ATPase, mainly in the myocardium. This inhibition causes an increase in intracellular sodium levels, resulting in a reversal of the action of the sodium-calcium exchanger, which causes an increase in the intracellular calcium concentration. This leads to a decrease in heart rate and increased storage of calcium in the sarcoplasmic reticulum, causing a corresponding increase in the release of calcium during each action potential.