Digoxin produces its positive inotropic effect in heart failure through which intracellular mechanism?

• A Inhibition of sarcolemmal Na+/K+-ATPase, indirectly increasing intracellular calcium ✓
• B Inhibition of phosphodiesterase type 3, raising cAMP
• C Activation of beta-1 receptors, increasing calcium entry through L-type channels
• D Sensitization of troponin C to extracellular calcium

Explanation

Digoxin reversibly inhibits the Na+/K+-ATPase pump, raising intracellular sodium. The reduced sodium gradient decreases calcium extrusion via NCX, so more calcium accumulates in the sarcoplasmic reticulum and is released on each beat, enhancing contractility. Option B describes milrinone, option C describes sympathomimetics such as dobutamine, and option D describes levosimendan-like calcium sensitization, none of which apply to cardiac glycosides.

Reference: Katzung Basic and Clinical Pharmacology, 15th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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