Digoxin toxicity in dogs: signs and risk factors
9-year-old Irish Setter with dilated cardiomyopathy and atrial fibrillation, treated with pimobendan, furosemide, benazepril and digoxin. He has had anorexia and vomiting for 4 days. ECG and blood work:
| Parameter | Result | Reference |
|---|---|---|
| Rhythm | Atrial fibrillation at 70 bpm with ventricular premature complexes in bigeminy | Controlled AF: 100–140 bpm in clinic |
| Creatinine | 2.6 mg/dL | 0.5–1.5 |
| Potassium | 3.0 mmol/L | 3.5–5.5 |
| Serum digoxin (8 h post-dose) | 3.4 ng/mL | 0.5–1.5 (therapeutic) |
Which statement is correct?
chevron_right Show answer and explanation
A. It is digoxin toxicity favoured by azotaemia and hypokalaemia: stop it, correct potassium and monitor the ECG
Correct. Digoxin is excreted by the kidneys, so azotaemia makes it accumulate, and hypokalaemia (from furosemide and vomiting) increases its binding to myocardial Na+/K+ ATPase. Gastrointestinal signs come first; new arrhythmias (bigeminy, AV block, ventricular tachycardia) indicate severe toxicity.
B. The anorexia is due to heart failure: increase digoxin to better control the AF
The ventricular rate is already low and the serum concentration is toxic. Increasing the dose could cause advanced AV block or a fatal ventricular arrhythmia.
C. Hypokalaemia protects against toxicity: it should not be corrected
The opposite is true: potassium competes with digoxin for the Na+/K+ ATPase, so hypokalaemia enhances toxicity. It must be corrected.
D. Treat the vomiting with an antiemetic and keep the dose, because serum concentration does not relate to toxicity
The correlation is not perfect, but 3.4 ng/mL is clearly in the toxic range and the signs fit. Masking the vomiting delays the diagnosis.
lightbulb Key takeaway
Digoxin has a narrow therapeutic margin: dose it on lean body weight, reduce it in kidney disease and measure serum concentration 7–10 days after starting or changing the dose, 6–8 hours after a dose. In a dog on digoxin, any vomiting or new arrhythmia is toxicity until proven otherwise.
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Updated: October 31, 2026 · Educational content for veterinary professionals. It does not replace current clinical guidelines or the judgement of the attending veterinarian.