Digoxin and Cardiac Glycosides

Background

Digoxin and cardiac glycosides (i.e. digitoxin, yellow oleander, lily of the valley, bufo toads) clinically produce nausea, vomiting, and malaise. They also cause yellow halos in visual fields as a chronic effect. The mechanism of action is blockade of Na/K ATPase which increases intracellular calcium levels to increase contractility. In acute toxicity, potassium levels are a marker of toxicity and the hyperkalemia seen with digoxin toxicity is not what is causing the fatality. Rather it is the level that signals to the clinician the significance of the block of Na/K ATP ase. In one study, 100% of patients with a potassium level of greater than 5.5 died, approximately 50% died with a level between 5 and 5.5 and everyone lived with a level below 5.0.

 

Evaluation

  • Physical Exam: Lethargy
  • Laboratory abnormalities: Hyperkalemia (acute)
  • ECG: Any abnormality (though Afib RVR is unlikely). Classic: Biventricular tachycardia

 

Management

  • Digoxin fab fragments (see criteria below)
  • Indications: hemodynamically unstable pts, pts with significant arrhythmias, and potassium 5.0 mEq/L
  • It can also be indicated for pts with high post distribution digoxin levels even if they are asymptomatic. However, please contact poison control/toxicology for guidance.
  • The dosing of digoxin fab fragments for number of vials is the (serum level times the weight of the patient in kg)/100 rounded up.
  • For pts with severe symptomatic bradycardia when digoxin fab fragments are not available, atropine is recommended, though there is a significantly probability that it will not be effective.
  • Given the sensitivity of the myocardium with digoxin, pacers can trigger significant dysrhythmias and only recommended if no access to digoxin fab fragments or fab fragment failure.

 

 

 

Quick reference dosing:

  • Digoxin fab fragments: Number of vials = [(serum level times the weight of the patient)/100] rounded up NOTE: In acute on chronic toxicity or chronic toxicity, please contact the Poison Center or Medical Toxicology for guidance as less vials may be recommended to try to avoid adverse events from worsening heart failure or atrial fibrillation.
  • Atropine (for severe symptomatic bradycardia if digoxin fab fragments are not available): 0.5 mg IVP every 3 to 5 minutes to a maximum of 3 mg