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Digoxin toxicity
Digoxin toxicity shows as nausea and vomiting, visual disturbance and arrhythmias in which a fast rhythm is combined with slow conduction; in acute poisoning potassium rises and predicts death, and the decisive treatment is specific antibodies (Fab).
Why it matters in the exam
Two pictures are asked: an older patient on digoxin who developed kidney failure or was given a diuretic, with nausea, confusion and yellow-green vision (chronic toxicity, usually with low potassium), and a deliberate ingestion of a large amount with vomiting and high potassium (acute toxicity). The question is when to give Fab and at what dose.
The typical ECG disturbances are premature ventricular beats and bigeminy, atrial tachycardia with block, accelerated junctional rhythm, AV block and bidirectional ventricular tachycardia — the last is almost diagnostic. A "scooped" ST segment only shows that the drug is being taken, not toxicity.
Remember that the blood level reflects toxicity only when it is taken at least six hours after the last dose, because the drug is still distributing into the tissues before then. Factors that precipitate chronic toxicity include kidney failure, hypokalaemia, hypomagnesaemia, old age and drugs that raise the level, such as amiodarone, verapamil and clarithromycin. After Fab, the total level on a routine assay cannot be interpreted, and follow-up relies on the clinical picture, potassium and the ECG.
Key points
- Nausea, yellow vision and confusion with an arrhythmia — think of digoxin.
- A fast rhythm with block, and bidirectional VT — almost diagnostic.
- High potassium in acute poisoning predicts death.
- Fab for life-threatening arrhythmias, potassium above 5.0 or organ damage.
- Level only at least six hours after the dose; after Fab the level cannot be interpreted.
Summary table
| Situation | Potassium | Picture | Treatment |
|---|---|---|---|
| Acute poisoning | High (predicts severity) | Vomiting, bradycardia, block, arrhythmias | Fab; usually 10 vials empirically |
| Chronic toxicity | Usually low or normal | Confusion, yellow-green vision, anorexia, kidney failure | Fab; usually 3–6 vials |
| Bradycardia | Variable | AV block | Atropine, Fab |
| Ventricular arrhythmia | Variable | Bidirectional VT, VF | Fab; lidocaine; low-energy shock if unavoidable |
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Sources
- Goldfrank's Toxicologic Emergencies, 11th edition (2019) — Cardioactive steroids
- Tintinalli's Emergency Medicine: A Comprehensive Study Guide, 9th edition (2020) — Digitalis glycosides
- DigiFab (digoxin immune Fab) prescribing information, current label — Dosage and administration
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-06. The text may contain errors; when in doubt, check the source.