Which drug is recognized as a cardiac glycoside?

A cardiac glycoside refers to a class of medications that are derived from the leaves of the foxglove plant and are primarily used in the treatment of various heart conditions, specifically to enhance the contractility of the heart muscle. Digoxin falls under this classification and is utilized clinically to manage heart failure and atrial fibrillation by increasing the force of cardiac contractions and controlling heart rate.

Dexamethasone and Triamterene do not share the cardiac glycoside properties or uses; Dexamethasone is a corticosteroid primarily used for its anti-inflammatory and immunosuppressive effects, while Triamterene is a potassium-sparing diuretic that is often used to treat hypertension and edema, not directly influencing heart contractility. Pantoprazole Sodium is a proton pump inhibitor used to treat gastrointestinal conditions such as GERD, and it does not have any applicability as a cardiac glycoside.

Thus, Digoxin is the correct choice because of its specific role in improving heart function through mechanisms characteristic of cardiac glycosides.