Digoxin Toxicity

Who gets digoxin toxicity?

• Significant interactions with P450 pathway can lead to accumulation. A thorough drug history including recent discontinuations is important.
  
• Toxicity can occur in patients on stable doses who develop renal failure because of accumulation
  
• Toxicity is increased in older patients and those with hypokalemia, hypernatremia, hypomagnesemia, hypercalcemia

Symptoms:

• Blurred vision, coloured haloes
• Confusion, fatigue, delerium, hallucinosis
  
• anorexia, nausea, vomitting, diarrhea, abdominal pain

ECG/Conduction abnormalities:

• Bradycardia
• Ventricular ectopy (PVCs, bigeminy, small runs of VT)
• AV block - 1st, 2nd, 3rd degree
  
• atrial tachcardias with 2:1, 3:2, 4:1, 6:1 or sometimes variable AV block
• Accelerated Junctional Rhythms (particularly with HR >60)
  
• VT/VF
  

Levels (measure 6-12h post last dose):

• Goal levels in heart failure are 0.65-1.1mmol/L
  
• Normal levels usually less than 2.6mmol/L; however, hypokalemia can lead to toxicity despite lower levels
• Levels greater than 3.9mmol/L are usually symptomatic

Treatment:

• Supportive care
• Symptomatic bradycardias usually respond to atropine
• Attempt to avoid pacing if possible (irritible myocardium)
• Attempt to avoid beta-agonists (irritible myocardium)
  
• Treat hypokalemia and hypomagnesemia
• Cautious treatment of hyperkalemia -- avoid calcium salts

"Digibind" - F(ab) fragments of engineered antibodies designed to bind to drug. For use in:

• Hemodynamically unstable
  
• Life threatening arrythmia
• Digoxin toxic rhytym with elevated digoxin level
  
• "Severe bradycardia"
• K+ >5 in acute ingestion
• dig level greater than 13 mmol/L or ingestion more than 10mg

Digibind will make further measurements of dig level inaccurate for >1 week. Ensure you dose it appropriately --> digoxin level x weight /100 = approximate # of vials.