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Key Features

Essentials of Diagnosis

  • Intoxication may result from

    • Acute single exposure

    • Chronic accumulation from accidental overmedication, especially in patients with kidney disease taking digoxin

  • Hyperkalemia common after acute overdose

  • Many different arrhythmias can occur

General Considerations

  • Cardiac glycosides paralyze the Na+-K+-ATPase pump and have potent vagotonic effects

  • Intracellular effects

    • Enhancement of calcium-dependent contractility

    • Shortening of the action potential duration

  • Older age and chronic kidney disease are associated with greater risk of digoxin toxicity

Clinical Findings

Symptoms and Signs

Acute overdose

  • Nausea and vomiting

  • Bradycardia

  • Atrioventricular (AV) block

  • Junctional rhythm common in patients with underlying atrial fibrillation

  • Hyperkalemia

Chronic overingestion

  • Hypokalemia and hypomagnesia are more likely owing to concurrent diuretic treatment

  • Ventricular arrhythmias; for example

    • Ectopy

    • Bidirectional ventricular tachycardia

    • Ventricular fibrillation

Differential Diagnosis

  • β-Blocker overdose

  • Calcium channel blocker overdose

  • Cardiotoxic plant or animal ingestion

    • Oleander

    • Foxglove

    • Lily of the valley

Diagnosis

Laboratory Tests

  • Serum digoxin level (Note: Levels drawn within 6 h of ingestion may be falsely elevated before complete tissue distribution)

  • Serum potassium (frequent measures useful because they correlate with tissue effects)

Diagnostic Procedures

  • Continuous ECG monitoring

  • Pacemaker may be needed

Treatment

Medications

Emergency measures

  • Ventricular arrhythmias: initially lidocaine, 2–3 mg/kg intravenously, or phenytoin, 10–15 mg/kg intravenously slowly over 30 min if digoxin-specific antibodies are not immediately available (see below)

  • Bradycardia: initially atropine, 0.5–2.0 mg intravenously, or transcutaneous external cardiac pacemaker

Gut decontamination

  • After acute overdose, administer activated charcoal, 60–100 g orally or via gastric tube, mixed in aqueous slurry

  • Emesis not recommended because it may enhance vagotonic effects (eg, bradycardia, AV block)

Activated charcoal

  • Repeated doses of activated charcoal, 20–30 g every 3–4 hours, may speed elimination of digitoxin (but not digoxin) by adsorbing drug excreted into gut lumen (gut dialysis)

  • Sorbitol or other cathartics should not be used with each dose; resulting large stool volumes may lead to dehydration or hypernatremia

Specific treatment

  • Severe intoxication: administer digoxin-specific antibodies [digoxin immune Fab (ovine) DigiFab]

  • Dose is estimated based on body burden of digoxin calculated from ingested dose or steady-state serum digoxin concentration

    • Ingested dose

      • Number of vials = ∼1.5–2 × ingested dose (mg)

    • Serum concentration

      • Number of vials = serum digoxin (ng/mL) × body weight (kg) × 10–2

      • Note: This is based on equilibrium digoxin level; after acute overdose, serum levels are falsely high for ...

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