DIGIFAB

Digoxin increases contractility of the myocardium by direct activity. The primary action of digoxin is specifically to inhibit adenosine triphosphatase, and thus sodium-potassium (Na+ - K+) exchange activity, the altered ionic distribution across the membrane resulting in an augmented calcium ion influx and thus an increase in the availability of calcium at the time of excitation-contraction coupling. The potency of digoxin may therefore appear considerably enhanced when the extracellular potassium concentration is low, with hyperkalaemia having the opposite effect.