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CDHB

Digoxin and other Cardiac Glycosides

• Acute poisoning:
  • Digoxin plasma concentration can be measured and may be useful.
  • Oleander, foxglove, lily of the valley and rhododendron all contain toxic glycosides.
  • Plasma potassium rises in proportion to toxicity.
• Chronic poisoning:
  • Digoxin levels may not be very high (tissue distribution).
  • Life-threatening toxicity is more common in the elderly with acute renal impairment or supra-therapeutic dosing.
  • Plasma potassium may be normal or low.
• Treatment:
  • Bradyarrhythmias:
    • Atropine IV to a maximum of 2 mg. May need pacing.
  • Tachyarrhythmias.
    • Magnesium sulphate 2-4 g IV.

      Note: If cardioversion (synchronised shock) is required, it may precipitate ventricular tachycardia/ventricular fibrillation, or asystole. Use low energy (10-25 joules). Seek Consultant advice.

  • Hyperkalaemia: Standard treatment, but avoid calcium as it may potentiate digoxin cardiotoxicity.
• Fab fragments (Digibind™ - kept in the Emergency Drug Cupboard):
  • Indications:
    • Life-threatening arrhythmias due to digoxin toxicity such as ventricular tachycardia, ventricular fibrillation, severe bradycardia not responding to atropine.
    • Severe hyperkalaemia refractory to insulin/glucose therapy.
  • Dosage for cardiac arrest or severe haemodynamic compromise:
    • 5 ampoules initially over 20 minutes in 100 mL sodium chloride 0.9% (10 amps if unstable).
    • If no response repeat dose.
    • If still no response in adults, see TOXINZ internet database and seek Consultant advice.
  • For dosage in less urgent clinical situations, see Digibind Drug insert.
  • Cautions following Fab fragments treatment:
    • Potassium levels can drop rapidly, check regularly.
    • Cardiac output may fall.
    • Ventricular rate may increase.

      Note: All patients should be monitored preferably in ICU/CCU if Fab fragments are used.

Topic Code: 1598