Digoxin

Action:
It causes a decrease in refractory period in atrial and ventricular cells of heart muscles. It causes an increase in effective refractory period and decreasing conduction velocity in AV node.

Therapeutic uses:
Atrial fibrillation and flutter (while controlling ventricular response rate).

Adverse effects:
It may cause ventricular beats originating from abnormal place. These beats may cause ventricular tachycardia and fibrillation. (treated with lidocaine or phenytoin)