Digoxin

Digoxin (Lanoxin®)

 

Class:
  • Cardiac glycoside
Actions:
  • Increases force of myocardial contraction (positive inotropic)
  • Decreased sympathetic tone
  • Increased urine production
  • Decreased renin release
  • Slows conduction through the AV node
  • Decreases automaticity in the SA node (negative chronotropic)
Indications:
  • Heart failure (left-sided or right-sided)
  • Atrial fibrillation or Atrial flutter (to decrease ventricular rate)
  • Supraventricular tachycardia
Pharmacokinetics:
  • Onset: 5-30 minutes (IV); 30 minutes – 2 hours (PO)
  • Peak:  1-4 hours (IV); 4-6 hours (PO)
  • Half-Life: 1.5 days
Adverse Effects:
  • Nausea, vomiting, anorexia, diarrhea
  • Fatigue, visual disturbances (e.g., blurred vision, yellow tinge to vision, halos around lights)
  • Prolonged PR interval, increased AV blocks
  • Confusion, drowsiness, dizziness, insomnia, nightmares
Signs of Toxicity:
  • Prolonged PR interval (1st degree AV block)
  • Signs of ventricular ectopy
  • Complaints of visual disturbances
  • (higher risk if patient has hypokalemia–low serum potassium)
Contraindications:
  • Digitalis hypersensitivity
  • Ventricular fibrillation
  • Ventricular tachycardia
  • Safety during pregnancy, lactation (Category A).
Dosages & Routes:
  • PO: (loading dose) 10-15 mcg/kg in divided doses over 24 – 48 hours
  • IV bolus:  (loading dose) 10-15 mcg/kg (1 mg) in divided doses over 24 hours
  • Maintenance Dose (IV or PO): 0.1 – 0.375 mg/day
Nursing Implications:
  • Drug Interactions:  1) Thiazide diuretics and loop diuretics promote dig-induced dysrhythmias by depleting potassium; 2) With digoxin, beta blockers and calcium channel blockers decrease contractility and heart rate; 3) Sympathomimetics (beta-adrenergic agonists) enhance heart rate and contractility; 4) Serum digoxin levels from oral doses are decreased by cholestyramine, kaolin-pectin, Neomycin, or sulfasalazine; 5) Serum digoxin levels are increased by aminoglycosides, colestipol, azithromycin, clarithromycin, erythromycin, omeprazole, tetracycline, alprazolam, amiodarone, captopril, diltiazem, nifedipine, nitrendipine, propafenone, quinidine, verapamil.
  • Drug IV Incompatibilities:  dobutamine, doxapram, amiodarone
  • Monitor blood pressure and apical pulse prior to administration.
  • Cardiac monitor should be used on patients receiving digoxin, especially loading doses.
  • Monitor serum digoxin levels closely, especially if receiving antibiotic therapy.
  • Monitor serum electrolytes, especially potassium.
  • Check for toxicity if visual or GI disturbances occur.
  • If DIGOXIN TOXICITY occurs with DYSRHYTHMIAS, 1) Discontinue any digitalis medications and any potassium depleting diuretics.  2) Check serum potassium level.  3) Phenytoin or lidocaine can be used as antidysrhythmic medications [Do Not Use Quinidine or Amiodarone.].  4) Atropine can be used for bradycardias or AV blocks.  5) Fab antibody agents (Digibind®) can be administered carefully intravenously.
  • Avoid electrical cardioversion if patient is receiving digoxin unless condition is life-threatening.  Then use lower doses (10-20 joules).
  • Emphasize to patient the importance of taking digoxin as prescribed at regular intervals and not missing doses.
  • Do not breast feed while taking digoxin.

 

References:

American Heart Association. (2006). Handbook of Emergency Cardiac Care (p. 49). Salem, MA: AHA.

Dirks, J.L. (2010) Cardiovascular therapeutic management.  In L.D. Urden, K.M. Stacy, & M.E. Lough's (Eds.) Critical care nursing: Diagnosis and management (6th ed., pp. 544-545).  St. Louis: Mosby Elsevier.

Lehne, R.A. (2010). Pharmacology for nursing care (7th ed., pp. 522-527, 548-549).  St. Louis: Saunders Elsevier.

Wilson, B.A., Shannon, M.T., Shields, K.M., & Stang, C.L. (2007).  Prentice Hall Nurse's Drug Guide 2007 (pp. 513-516).  Upper Saddle River, NJ: Pearson Prentice Hall.

 

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