Digoxin

Digoxin is a cardiac glycoside used in the treat of atrial arrhythmias and in cardiac failure as a positive inotrope.

Digoxin has both a direct and indirect mechanism of action:

  • Direct
    Inhibits cardiac Na+/K+ ATPase, causing:
    • Increasing intracellular [Na+], increasing activity of the Na+/Ca2+ pump
    • Increased intracellular Ca2+ increases inotropy
    • Decreased K+ results prolongs refractory period of the AV node and bundle of His
  • Indirect
    Parasympathomimetic effects by increasing ACh release at cardiac muscarinic receptors.
    • Slows AV nodal conduction and ventricular response
      This improves coronary blood flow, increasing time for ventricular filling, and improving cardiac output.
Property Action
Class Cardiac Glycoside
Uses Arrhythmia - particularly AF/Flutter, and CCF
Presentation Tablets, elixir, clear colourless solution
Route of Administration PO/IV
Dosing PO: 62.5μg-250μg, IV: 250-500μg load
Absorption >70% bioavailability though varies with formulation
Distribution 25% protein bound. VD 5-11L.kg-1, dependent on lean mass
Metabolism Minimal hepatic metabolism
Elimination Renal elimination of active metabolites t1/2 35 hours - increased in renal failure
CVS HR, ↑ inotropy, arrhythmias including; bigeminy, PVCs, 1st/2nd/3rd degree AV block, SVT, VT
CNS Deranged red-green colour perception, visual disturbances, headache
Immune Eosinophilia and rash
Metabolic Gynaecomastia
Toxic Effects Narrow TI. Severe arrhythmia with DC cardioversion

Interactions

Interaction Drug
Increased level Amiodarone, captopril, erythromycin, verapamil
Decreased level Antacids, cholestyramine, phenytoin, metoclopramide

References

  1. Peck TE, Hill SA. Pharmacology for Anaesthesia and Intensive Care. 4th Ed. Cambridge University Press. 2014.
Last updated 2018-09-21

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