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Anna Lee

First posted June 2006

Pharmacokinetics

  • Bioavailability 75%

  • 60% renal elimination

  • Large volume of distribution 5-7 L/kg

Clinical Toxicity

Cardiac

  • chief effects are on heart and consist of ventricular arrhythmias (due to enhances automaticity) in combination with heart block (due to increase vagal tone). Any arrhythmia is possible except a rapidly conducted supraventricular rhythm

Extracardiac

  • Gastrointestinal – nausea and vomiting are common

  • CNS – headache, confusion, visual disturbances. Seizures very rare

  • Metabolic – hyperkalaemia due to blockade of Na/K ATPas, is a bad prognostic sign.

    • K< 5 mmol/l – all survive

    • 5 < K < 5.5 mmol/l – 50% survive

    • K > 5.5 mmol/l – all die

Management

  • Gastric lavage not recommended because of risk of arrhythmia from increased vagal tone

  • Multi-dose activated charcoal adsorbs digoxin well

  • Internal electrical pacing is controversial, might cause arrhythmia and increase mortality. Atropine can be used to treat heart block

  • Treat arrhythmias as they arise. Phenytoin is first choice for ventricular arrhythmias. Amiodarone or lignocaine if phenytoin fails ; Avoid class 1A, 1C, II and IV antidysrhythmics. Cardioversion may precipitate refractory VT, VF or asystole. Should be used if necessary, and always start at low-energy shocks (10-25J).

Digoxin-Specific Antibody Fragments

Indications:

  • ventricular dysrhythmias

  • bradycardia not responsive to atropine

  • serum K > 5 mmol/l

  • serum digoxin 13-19.5 nmol/L in an acute ingestion

  • digoxin ingestion >10mg

 Give as infusion over 20 min. Onset time ranges from before to 30 min after end of infusion. Adverse effects are mostly due to effects of reversing digoxin: hypokalaemia, fast AF, heart failure. Administration of antibody may interfere with subsequent measurement of plasma or serum digitalis concentration

 © Anna Lee, June 2006

©Charles Gomersall, August, 2008 unless otherwise stated. The author, editor and The Chinese University of Hong Kong take no responsibility for any adverse event resulting from the use of this webpage.
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