1. The most frequent use of digitalis is in the treatment of congestive heart failure. Digitalis blocks the sodium-potassium ATP-ase pump of the cardiac muscle so that intracellular concentration of sodium is increased. This leads to increase in calcium ions, released from sarcolemma and thereby, brushing action of proteins viz. actin and myosin is enhanced. This is exhibited as more forceful contractions of myocardium, greater output per beat and complete emptying of heart. Due to this, the delayed circulation in congestive heart failure is improved and the oedema is flushed out. Digitalis shortens the length of systole, thereby giving more time to rest between contractions.
2. Another major use of digitalis is slowing ventricular rate in atrial fibrillation, atrial, flutter, supraventricular tachycardia and premature extra systoles. This is due to negative chronotropic effect (slowing the heart rate) by directly suppressing the conduction of electric impulses at auriculo- ventricular node.

Dose

Initial dose - 1 - 2 g in 24 - 48 hours
Maintenance - 100 mg daily