Cardiac glycosides are drugs used in the treatment of congestive heart failure (CHF) or cardiac arrhythmia, by inhibiting the Na⁺/K⁺ pump. This inhibition increases the amount of Ca⁺⁺ ions available for contraction and improves cardiac output and reduces distention of the heart.

Cardiac glycosides are extracted from plant material :

• strophantus - ouabaine
• digitalis lanata and digitalis purpurea - digoxin, digitoxin
• scilla maritima - proscillaridine A

It has an antiarrhythmic effect by prolonging the refractory period of the AV node (Atrio-ventricular), reducing the number of impulses reaching the ventricles. Cardiac output is restored but atrial fibrillation or atrial flutter are not abolished.