Amiodarone in dogs: hepatotoxicity and monitoring
7-year-old Great Dane with dilated cardiomyopathy and ventricular tachycardia refractory to sotalol, on oral amiodarone for 10 weeks. He now has anorexia and lethargy; the rhythm is controlled. Blood work:
| Parameter | Result | Reference |
|---|---|---|
| ALT | 820 U/L | 10–100 |
| Alkaline phosphatase | 640 U/L | 20–150 |
| Total bilirubin | 0.4 mg/dL | 0.1–0.5 |
| ALT before starting | 45 U/L | 10–100 |
| Total T4 | 0.9 µg/dL | 1.0–4.0 |
What is the interpretation and the most appropriate approach?
chevron_right Show answer and explanation
A. Stress-related vacuolar hepatopathy: keep the dose and recheck in three months
ALT has risen from 45 to 820 U/L after starting a drug known for hepatotoxicity, and there are clinical signs. Waiting three months on the same dose risks severe liver injury.
B. Amiodarone only causes adverse effects after years of use: look for another cause
In dogs hepatotoxicity can appear within weeks or a few months. That is why ALT is monitored from the start of treatment.
C. Drug-induced hypothyroidism: add levothyroxine and continue amiodarone
Amiodarone can alter thyroid function, but a slightly low T4 in a sick dog does not explain the anorexia or the ALT. Hepatotoxicity is the priority.
D. Amiodarone hepatotoxicity: reduce or stop the drug and monitor liver enzymes
Correct. Raised ALT is the most common adverse effect of amiodarone in dogs and may be accompanied by anorexia. It is usually reversible after reducing or stopping the drug. If the arrhythmia demands it, another antiarrhythmic is considered with the cardiologist.
lightbulb Key takeaway
Amiodarone is useful for refractory arrhythmias, but in dogs ALT, a complete blood count (neutropenia, thrombocytopenia) and T4 must be monitored from the start. Its half-life is very long: both effect and toxicity take weeks to appear and to resolve.
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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.