Amiodarone
Amiodarone hydrochloride
Also known as: Cordarone · Pacerone · Nexterone · amiodaroni hydrochloridum · L3428 · 51087N · SKF-33134-A · Amiodaronum
Reviewed by the VetSheet Veterinary TeamUpdated Apr 5, 2026Evidence-based veterinary reference
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Dosing by species
🌎 NA — North America🌍 EU — Europe
Dogs
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| For atrial fibrillation or ventricular arrhythmias primarily in ambulatory patients | 8-10 mg/kg PO every 12 hours | PO | q12h | — | 🌎 NA |
| For ventricular arrhythmias secondary to occult cardiomyopathy in Doberman pinschers | 10 mg/kg PO twice daily for one week and then 8 mg/kg PO once daily. After 6 months reduce to 5 mg/kg PO once daily. | PO | q12h then q24h | Long-term | 🌎 NA |
| For ventricular tachycardia when other first line drugs (Class I antiarrhythmics ± beta-blockers) are ineffective | 10 mg/kg PO q12h for one week and then 5 mg/kg PO q12h for maintenance. | PO | q12h | Long-term | 🌎 NA |
| For SVTs or Vtach | 10-20 mg/kg PO once daily (q24h) loading for 5-7 days; 5-10 mg/kg PO once daily thereafter. | PO | q24h | Long-term | 🌎 NA |
| Ventricular and supraventricular arrhythmias, atrial fibrillation, ventricular pre-excitation syndromes | Dose not specified in monograph | PO/IV | Not specified | Not specified | 🌍 EU |
- For atrial fibrillation or ventricular arrhythmias primarily in ambulatory patients: Use caution if patient has bradycardia, AV blocks, or thyroid disorders.
- For ventricular arrhythmias secondary to occult cardiomyopathy in Doberman pinschers: For severe V-Tach, mexiletine is added at 5-8 mg/kg three times daily for one week. Once efficacy confirmed, patient weaned off mexiletine.
- Ventricular and supraventricular arrhythmias, atrial fibrillation, ventricular pre-excitation syndromes: Use as an IV infusion for recent onset atrial fibrillation has variable efficacy for restoring sinus rhythm but a high frequency of severe adverse effects.
Horses
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| For conversion of atrial fibrillation or ventricular tachycardia | 5 mg/kg/hr for one hour, followed by 0.83 mg/kg/hr for 23 hours and then 1.9 mg/kg/hour for the following 30 hours. | IV | CRI | Up to 54 hours | 🌎 NA |
- For conversion of atrial fibrillation or ventricular tachycardia: Infusion was discontinued when conversion occurred or when any side effects were noted. Regimen should be further adapted based upon PK/PD studies.
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Overview
Amiodarone is a potent, broad-spectrum Class III antiarrhythmic agent used primarily for severe, refractory ventricular and supraventricular arrhythmias.
Because of its complex pharmacokinetic profile and significant potential for toxicity, it is generally reserved for cases where conventional, less toxic therapies have failed.
Clinical Pearls:
- Structurally, amiodarone is an iodinated benzofuran derivative. A 200 mg tablet contains approximately 75 mg of iodine, which can impact thyroid function.
- It is highly lipophilic, leading to extensive tissue distribution and accumulation in adipose tissue, which contributes to its exceptionally long and variable half-life.
- In veterinary medicine, it is most notably used in Doberman Pinschers with occult dilated cardiomyopathy (DCM) presenting with rapid, wide-complex ventricular tachycardia or syncope.
- Due to the high risk of adverse effects (including hepatotoxicity and thyroid dysfunction), rigorous monitoring is essential.
Mechanism of action
Amiodarone is uniquely versatile, possessing properties of all four Vaughan-Williams antiarrhythmic classes, though it is primarily classified as a Class III agent.
- Class III (Primary): Blocks potassium (K+) channels → prolongs phase 3 repolarization, action-potential duration (APD), and the effective refractory period (ERP) in myocardial cells.
- Class I: Blocks fast sodium (Na+) channels → slows conduction velocity.
- Class II: Non-competitively blocks beta-adrenergic receptors → provides sympatholytic effects, reducing heart rate.
- Class IV: Weakly blocks calcium (Ca2+) channels → slows AV node conduction and suppresses automaticity.
It is metabolized in the liver to its active metabolite, desethylamiodarone, which also contributes significantly to its antiarrhythmic effects.
Safety & warnings
Contraindications
- Hypersensitivity to amiodarone or iodine
- Severe sinus-node dysfunction
- Severe sinus bradycardia
- 2nd or 3rd degree AV block
- Bradycardial syncope
Adverse effects
- Vomiting
- Anorexia
- Hepatopathy (elevated liver enzymes, bilirubinemia)
- Bradycardia
- Neutropenia
- Thrombocytopenia
- Positive Coombs' test
- Corneal deposits
- Injection site pain (IV)
- Facial pruritus and hyperemia (IV)
- Hind limb weakness (horses)
- Diarrhea (horses)
Precautions
High Toxicity Potential: Clinical experience in veterinary patients is limited. Use only when other less toxic and more commonly used drugs are ineffective.
- Hepatic Effects: Hepatopathy can occur before clinical signs are noted; routine serial evaluation of liver enzymes and bilirubin is strongly recommended.
- Thyroid Function: May alter thyroid hormone levels (increases T4 and reverse T3, decreases T3) due to high iodine content.
- Pregnancy: FDA Category D. Embryotoxic in laboratory animals; congenital thyroid abnormalities detected in offspring. Use only if benefits outweigh risks.
Drug interactions
Significantly increases serum levels and/or pharmacologic/toxic effects of the anticoagulant.
Significantly increases serum levels and/or toxic effects of digoxin.
Increases cyclosporine levels; may increase creatinine.
Significantly increases serum levels and/or toxic effects of lidocaine.
Significantly increases serum levels and/or toxic effects with prolonged amiodarone administration.
Significantly increases serum levels and/or toxic effects of phenytoin.
Significantly increases serum levels and/or toxic effects of procainamide.
Significantly increases serum levels and/or toxic effects of quinidine.
Additive effects on QTc interval; possible serious arrhythmias.
Additive effects on QTc interval; possible serious arrhythmias.
Additive effects on QTc interval; possible serious arrhythmias.
Additive effects on QTc interval; possible serious arrhythmias.
Additive effects on QTc interval; possible serious arrhythmias.
Additive effects on QTc interval; possible serious arrhythmias.
Additive effects on QTc interval; possible serious arrhythmias.
Increased risks for hypotension or arrhythmias.
Possible potentiation of bradycardia, AV block, or sinus arrest.
Possible potentiation of bradycardia, AV block, or sinus arrest.
Increased amiodarone levels.
Possible hypotension, bradycardia.
Decreased amiodarone levels.
May significantly increase serum levels and/or pharmacological effects
May significantly increase serum levels and/or pharmacological effects
May significantly increase serum levels and/or pharmacological effects
May significantly increase serum levels and/or pharmacological effects
May significantly increase serum levels and/or pharmacological effects
Monitoring
- ECG (for antiarrhythmic efficacy and proarrhythmic effects)
- Gastrointestinal signs (anorexia, vomiting)
- CBC (for neutropenia, thrombocytopenia)
- Serial liver enzymes and bilirubin (baseline and routine monitoring)
- Thyroid function tests
- Blood pressure
- Pulmonary radiographs (if clinical signs such as dyspnea or cough occur)
Pharmacokinetics
Half-life
Absorption
Oral absorption is slow and variable. In horses, oral bioavailability is low (6-34%). In humans, bioavailability ranges from 22-86%.
Distribution
Widely distributed throughout the body and highly lipophilic, accumulating in adipose tissue. In horses, it has a high apparent volume of distribution (31 L/kg) and is highly bound to plasma proteins (96%).
Metabolism
Metabolized by the liver into the active metabolite desethylamiodarone.
Elimination
Clearance in horses is 0.35 L/kg/hr. Neither amiodarone nor its active metabolite are dialyzable.
Overdose
Clinical overdosage experience is limited.
Expected Signs:
- Hypotension
- Bradycardia
- Cardiogenic shock
- AV block
- Hepatotoxicity
Treatment:
- Therapy is primarily supportive.
- Bradycardia may be managed with a pacemaker or beta-1 agonists (e.g., isoproterenol).
- Hypotension may be managed with positive inotropic agents or vasopressors.
- Note: Neither amiodarone nor its active metabolite are dialyzable.
Available products
Formulations
- Oral tablets
- Injection solution
- Compounded oral suspension
Human-labeled
- Amiodarone Oral Tablets: 100 mg, 200 mg & 400 mg (Cordarone, Pacerone, generic)
- Amiodarone Injection Solution: 50 mg/mL in 3 mL, 10 mL & 30 mL single-dose vials, 18 mL multiple-dose vials & 3 mL prefilled syringes (Nexterone, generic)
Regulatory status
Human-approved products used off-label under the cascade.
POM (Prescription Only Medicine). Used under the prescribing cascade.
No regulatory data for: 🇺🇸 US · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
Storage & stability
Tablets should be stored in tight containers at room temperature and protected from light. Injection should be stored at room temperature and protected from light or excessive heat (light protection is not necessary during active IV administration). Compounded oral suspension (5 mg/mL in Ora-Plus/Ora-Sweet) retains >90% potency for 91 days when stored at 5°C and protected from light.
Client information
Your pet has been prescribed amiodarone to treat a serious, potentially life-threatening heart rhythm abnormality. Because this is a very potent medication, careful monitoring is required.
- Informed Consent: Because experience with this drug in pets is limited and it carries a risk of toxicity, your veterinarian will discuss the risks and benefits with you before starting treatment.
- Administration: Give exactly as prescribed. Do not skip doses or stop the medication abruptly without consulting your veterinarian.
- Side Effects to Watch For: Contact your veterinarian immediately if your pet stops eating, vomits, seems unusually lethargic, develops a cough, or has difficulty breathing.
- Follow-up Testing: Your pet will need regular blood tests to monitor liver and thyroid function, as well as periodic ECGs to ensure the drug is working safely.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturer’s current label.