Digitoxin is a purified cardiac glycoside similar in structure and function to Digoxin. Unlike Digoxin, Digitoxin is eliminated from the body via the liver and not the kidneys. Both drugs are used to treat various heart conditions. Cardiac glycosides bind to a site on the extracellular aspect of the a-subunit of the Na+/K+ ATPase pump in the membranes of heart cells (myocytes). This causes an increase in the level of sodium ions in the myocytes, which then leads to a rise in the level of calcium ions.