Critical Care Trauma Centre

DIGOXIN (Lanoxin)

 

Name: DIGOXIN (LanoxinR)
Classification: cardiac glycoside
  • used in treatment of atrial fibrillation, atrial flutter, atrial tachycardia
  • positive inotrope, negative chronotrope, negative dromotrope
  • used to improve cardiac output in congestive heart failure
Dose:
  • for congestive heart failure:
    • loading dose: 8 - 10 mcg/kg lean body weight
    • half of total dose given as first dose and additional fractions are given at 6 to 8 hour intervals
  • maintenance dose: 
    • 1/3 of loading dose given once per day
  • for atrial fibrillation:
    • loading dose: 10 - 15 mcg/kg lean body weight administered as above

Reduce dosage in renal failure, hypothyroidism
 

Creatinine Clearance Dose Reduction

10-50 mL/minute

(0.17-0.84 mL/second)

Administer 25-75% of daily dose divided at normal intervals or give the normal dose every 36 hours.

Less than 10 mL/minute

(0.17 mL/second)

Administer 10-25% of daily dose divided at normal intervals or give the normal dose every 48 hours.

IV conversion dose is generally 80% of oral dose

Administration: IV Direct:
  • Mix in 50 mL of D5W or NS and administer over 5 - 10 minutes
  • dilute with four times or greater volume to avoid precipitation
  • onset of action 5 - 30 minutes post IV bolus
  • rapid infusion may cause systemic or coronary artery vasoconstriction
Adverse Effects:

Symptoms of Toxicity:

Cardiac effects:

  • every type of arrhythmia or AV block (sinus bradycardia or sinus rhythm with AV block, PAT with block, atrial fibrillation with complete heart block very suggestive of digoxin toxicity)
  • risk factors:
    • potassium/magnesium deficiencies or hypercalcemia increase risk of toxicity
    • febrile or hypermetabolism-induced atrial arrhythmias may be resistant to digoxin, predisposing to toxicity
  • gastrointestinal effects: anorexia, nausea, vomiting, diarrhea(common early signs of toxicity)
  • CNS: headache, fatigue, lethargy, drowsiness, generalized muscle weakness, vertigo, neuralgia
  • Occular: 'yellow and green' halo vision, diplopia, photophobia, blurred vision 
     
Effects on potassium:
  • chronic toxicity: hypokalemia 
  • acute toxicity: hyperkalemia
  • Low magnesium, low potassium and hypercalcemia predispose patient to digoxin toxicity
Antidote: Antidote for digoxin toxicity: Digoxin Immune Fab (Ovine)
Drug Interactions:
  • Reduce dosage in renal failure and hypothyroidism
  • In renal failure
  • beta blockers + digoxin = increased digoxin toxicity, decreased inotropic effect
  • calcium + digoxin = increased risk of arrhythmias
  • verapamil + digoxin = increased digoxin level
  • propafenone + digoxin = decreased inotropic effect
  • quinidine + digoxin = increased digoxin level
  • rifampin + digoxin = decreased digoxin level
  • sympathomimetics + digoxin = increased risk of arrhythmias
  • drugs which cause hypokalemia = increased risk of digoxin toxicity
Monitoring Therapy:
  • continuous heart rate and rhythm for acutely ill patients or during loading
  • PR interval
  • blood pressure
  • potassium, magnesium and calcium levels
  • urea, creatinine
  • urine output
  • routine levels not indicated; dosage adjustments should be based on symptomatology
  • for chronic dosing, check pulse rate prior to administration of each dose
Adult Critical Care Protocol:
  • May be administered IV direct or by IV infusion by a nurse in Adult Critical Care
  • Continuous infusions must be administered by infusion device and the pump library must be enabled.


Lynne Kelly, Pharmacist, CCTC
Brenda Morgan, Clinical Nurse Specialist, CCTC
Last Update: October 11, 2018