NAPLEX Practice Question # 88

NAPLEX Examination.

Practice Question # 88.


Digoxin (Lanoxin®)

  • Digoxin belongs to the cardiac glycoside family of positive ionotropic agents and is composed of a steroidal nucleus, an unsaturated lactone ring, and three sugars attached via glycosidic linkage (Figure 10-10). Th e glycoside portion is required for function, and bacterial cleavage of the glycosidic bond in the gastrointestinal (GI) tract reduces effi cacy in about 10% of the population.
  • Digoxin inhibits the actions of the electrogenic Na/K-ATPase resulting in increased intracellular Na and consequent increase in intracellular calcium via actions of the coupled Na-Ca2 exchanger. Th is intracellular calcium is stored in the sarcoplasmic reticulum until myocardial depolarization produces greater calcium-induced calcium release, which produces enhanced cardiac contractility.
  • Improved cardiac contractility leads to increased cardiac output, better tissue perfusion, and enhanced renal function and urine output. Th is promotes greater water loss and reduces pulmonary congestion and edema of the extremities.

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