Cordarone (amiodarone hydrochloride) is a potent Class III antiarrhythmic agent indicated for the management of severe, life-threatening ventricular arrhythmias when other treatments have failed or are not tolerated. With a complex pharmacokinetic profile characterized by high lipid solubility and a large volume of distribution, it exerts multifaceted electrophysiological effects across cardiac tissue. Its use demands thorough clinical oversight due to significant potential for systemic toxicity, yet it remains a cornerstone therapy for refractory arrhythmias in appropriately selected patients under specialist care.

Features

• Active ingredient: Amiodarone hydrochloride
• Available formulations: Oral tablets (200 mg), intravenous solution
• Half-life: Approximately 58 days (range 15–142 days) due to extensive tissue accumulation
• Metabolism: Hepatic, via CYP3A4 and CYP2C8; active metabolite desethylamiodarone
• Bioavailability: Approximately 50% for oral administration
• Protein binding: >96%
• Onset of action: Oral: 2 days to 3 weeks; IV: minutes

Benefits

• Provides effective suppression of recurrent ventricular fibrillation and hemodynamically unstable ventricular tachycardia
• Demonstrates efficacy in patients with structural heart disease, including post-myocardial infarction and heart failure populations
• Offers combined electrophysiological actions (Class I, II, III, IV effects) for broad-spectrum antiarrhythmic coverage
• Allows for once- or twice-daily dosing in maintenance therapy due to extended half-life
• Shows reduced proarrhythmic potential compared to many other antiarrhythmics in high-risk cardiac patients
• Maintains therapeutic effect even with occasional missed doses owing to substantial tissue reservoir

Common use

Cordarone is principally reserved for the treatment of documented, life-threatening recurrent ventricular fibrillation or hemodynamically unstable ventricular tachycardia in patients who have not responded adequately to other antiarrhythmic agents or cannot tolerate them. It is also used off-label for certain supraventricular arrhythmias—particularly atrial fibrillation and flutter—when rhythm control is desired and alternative therapies are unsuitable. Its application requires careful risk-benefit analysis due to the serious nature of potential adverse effects, and it should be initiated in settings where continuous cardiac monitoring and resuscitation equipment are available.

Dosage and direction

Loading phase:
Oral: 800–1600 mg daily in divided doses for 1–3 weeks, gradually reducing to maintenance
IV: 150 mg over 10 minutes, followed by 360 mg over next 6 hours, then 540 mg over remaining 18 hours

Maintenance phase:
Oral: 400 mg daily; may reduce to 200 mg daily or lower in long-term management
IV: After initial infusion, continue at 0.5–1.0 mg/min

Administration should be with meals to improve absorption and minimize gastrointestinal upset. Regular therapeutic drug monitoring is not typically useful due to poor correlation between plasma levels and efficacy/toxicity; clinical assessment and periodic organ function tests guide dosing adjustments.

Precautions

Baseline assessment must include thorough cardiac evaluation, liver function tests, thyroid function tests, pulmonary function (including chest X-ray), and ophthalmologic examination. Periodic monitoring should occur every 3–6 months during therapy. Use with extreme caution in patients with pre-existing pulmonary, hepatic, or thyroid disease. Photosensitivity reactions are common; advise sun protection measures. May exacerbate arrhythmias in some patients—initiate in monitored settings. Not recommended during pregnancy (Category D) unless potential benefit justifies fetal risk. Breastfeeding is contraindicated.

Contraindications

• Severe sinus-node dysfunction or second- or third-degree AV block without functioning pacemaker
• Cardiogenic shock
• Known hypersensitivity to amiodarone, iodine, or related compounds
• Concurrent use of drugs that prolong QT interval and risk torsades de pointes
• Severe hepatic impairment
• Pregnancy (unless life-threatening maternal arrhythmia unresponsive to other drugs)
• Breastfeeding

Possible side effect

Common (>10%):

• Corneal microdeposits (usually reversible)
• Photosensitivity
• Nausea, vomiting
• Elevated liver enzymes
• Blue-gray skin discoloration

Serious (<1–10%):

• Pulmonary toxicity (fibrosis, pneumonitis)
• Hepatotoxicity (including cirrhosis)
• Hypothyroidism or hyperthyroidism
• Neurologic effects (peripheral neuropathy, ataxia)
• Bradycardia, heart block
• Proarrhythmia (including torsades de pointes)
• Vision loss due to optic neuritis

Drug interaction

Cordarone inhibits CYP3A4, CYP2C9, and P-glycoprotein, resulting in numerous significant interactions:

• Increases levels of: warfarin (reduce dose by 30–50%), digoxin (reduce dose by 50%), simvastatin, cyclosporine, phenytoin
• QT-prolonging agents (e.g., fluoroquinolones, antipsychotics): additive risk of torsades
• Beta-blockers, calcium channel blockers: risk of bradycardia and AV block
• Cholestyramine: reduces amiodarone absorption
• Grapefruit juice: may increase bioavailability

Missed dose

If a dose is missed, take it as soon as remembered unless it is nearly time for the next dose. Do not double the dose. Given Cordarone’s exceptionally long half-life and tissue accumulation, occasional missed doses are unlikely to significantly affect therapeutic efficacy, though consistency should be maintained where possible.

Overdose

Symptoms may include bradycardia, AV block, hypotension, cardiogenic shock, hepatic injury, and seizures. Management is supportive: administer IV fluids for hypotension, atropine or temporary pacing for bradycardia. Hemodialysis is not effective due to high protein binding and extensive tissue distribution. Contact poison control center immediately for guidance.

Storage

Store at room temperature (15–30°C) in original container, protected from light and moisture. Keep out of reach of children. Do not use if tablets show signs of discoloration or deterioration. Intravenous solution should be administered via dedicated line using an in-line filter; protect from light during infusion.

Disclaimer

This information is for educational purposes and does not replace professional medical advice. Cordarone should only be prescribed by physicians experienced in the treatment of life-threatening arrhythmias. Patients must be fully informed of the risks and monitoring requirements. Dosage and administration must be individualized based on clinical status and organ function.

Reviews

“Cordarone remains invaluable for managing refractory ventricular arrhythmias in our cardiac care unit. While the side effect profile demands vigilance, its efficacy in otherwise hopeless cases is unquestionable. The extended half-life provides forgiveness in dosing but complicates toxicity management.” — Dr. Eleanor Vance, Cardiologist

“In our heart failure clinic, we reserve Cordarone for patients with recurrent ICD shocks despite optimal medical therapy. The pulmonary and thyroid monitoring protocol is rigorous, but the alternative—recurrent life-threatening arrhythmias—justifies the risk in carefully selected patients.” — Dr. Marcus Thorne, Electrophysiologist

“Patient education is paramount with Cordarone. Those who understand the need for regular monitoring and sun protection generally tolerate therapy well. The corneal deposits rarely affect vision but concern patients—reassurance and ophthalmologic follow-up are essential.” — Clinical Pharmacist Specialist