Cordarone (amiodarone hydrochloride) is a potent Class III antiarrhythmic agent indicated for the management of severe ventricular and supraventricular arrhythmias. With a complex pharmacokinetic profile characterized by high lipid solubility and a large volume of distribution, it demonstrates efficacy in cases refractory to other antiarrhythmic therapies. Its unique mechanism involves prolonging the action potential duration and effective refractory period through potassium channel blockade, while also exhibiting sodium channel blockade, noncompetitive β-adrenergic inhibition, and weak calcium channel blocking activity. Medical supervision is mandatory throughout treatment due to its significant side effect profile and potential for serious interactions.

Features

• Active ingredient: Amiodarone hydrochloride
• Available formulations: 200 mg oral tablets; 150 mg/3 mL intravenous solution
• Half-life: Approximately 58 days (range 15-142 days) due to extensive tissue distribution
• Bioavailability: Approximately 50% with considerable interindividual variation
• Metabolism: Hepatic via CYP3A4 and CYP2C8; active metabolite (desethylamiodarone)
• Excretion: Primarily biliary; negligible renal excretion
• Onset of action: Oral: 2 days to 3 weeks; IV: minutes to hours

Benefits

• Effective suppression of life-threatening ventricular arrhythmias including ventricular tachycardia and fibrillation
• Maintenance of sinus rhythm in patients with atrial fibrillation/flutter where other agents have failed
• Reduced hospitalization rates for arrhythmia recurrence compared to many alternative antiarrhythmics
• Demonstrated efficacy in patients with structural heart disease including post-MI and heart failure
• Single daily dosing possible during maintenance phase due to extended half-life
• Available in both oral and intravenous formulations for flexible administration

Common use

Cordarone is primarily prescribed for the treatment of documented, life-threatening recurrent ventricular fibrillation and recurrent hemodynamically unstable ventricular tachycardia when these arrhythmias have not responded to adequate doses of other antiarrhythmics or when alternative agents are not tolerated. It is also used for the conversion of atrial fibrillation to sinus rhythm and maintenance of sinus rhythm after conversion in patients with symptomatic atrial fibrillation/flutter. Off-label uses include treatment of other supraventricular tachyarrhythmias and as adjunctive therapy in electrical storm. Its use is generally reserved for situations where the benefit outweighs the significant risk of adverse effects.

Dosage and direction

Loading dose (oral): 800-1600 mg daily in divided doses for 1-3 weeks until adequate arrhythmia control is achieved or side effects occur. Maintenance dose: Typically 400 mg daily, though may be reduced to 200 mg daily or increased to 600 mg daily based on response and tolerance. Intravenous loading: 150 mg over 10 minutes followed by 360 mg over next 6 hours, then 540 mg over remaining 18 hours. Maintenance IV infusion: 0.5-1.0 mg/minute. Administration with meals may reduce gastrointestinal upset. Regular monitoring of thyroid function, liver enzymes, pulmonary function, and electrocardiograms is essential throughout therapy. Dose adjustments are necessary in elderly patients and those with hepatic impairment.

Precautions

Baseline assessment must include complete cardiac evaluation, pulmonary function tests, liver function tests, thyroid function tests, and ophthalmologic examination. Periodic monitoring should occur at least every 3-6 months during therapy. Use with extreme caution in patients with pre-existing pulmonary disease, hepatic impairment, or thyroid disorders. Photosensitivity reactions are common; patients should use protective clothing and high-SPF sunscreen. Corneal microdeposits develop in most patients; regular ophthalmologic follow-up is recommended. May exacerbate arrhythmias; initial hospital monitoring is advised during loading phase. Pregnancy Category D; use only if potential benefit justifies potential fetal risk. Breastfeeding is not recommended due to secretion in milk.

Contraindications

Absolute contraindications include known hypersensitivity to amiodarone or iodine, severe sinus node dysfunction resulting in marked sinus bradycardia unless artificial pacemaker is present, second- or third-degree AV block unless artificial pacemaker is present, and bradycardia leading to syncope. Relative contraindications include severe hepatic impairment, pulmonary fibrosis or interstitial lung disease, uncorrected electrolyte imbalances (particularly hypokalemia and hypomagnesemia), and concomitant use with drugs that prolong QT interval or may cause torsades de pointes. Should not be used as first-line therapy for atrial fibrillation due to toxicity profile.

Possible side effect

Common (>10%): Corneal microdeposits (usually reversible), photosensitivity, nausea, vomiting, fatigue, tremor/ataxia, blue-gray skin discoloration. Serious but less common: Pulmonary toxicity (2-17% including interstitial pneumonitis, ARDS, pulmonary fibrosis), hepatotoxicity (elevated transaminases 15-30%, clinical hepatitis 3%), hypothyroidism (6%) or hyperthyroidism (2%), peripheral neuropathy (0.3% annually), optic neuritis/neuropathy. Cardiac: Bradycardia, QT prolongation, heart block, worsening heart failure. Rare but severe: Stevens-Johnson syndrome, toxic epidermal necrolysis, bronchospasm, neutropenia. Most adverse effects are dose-related and may appear months after initiation.

Drug interaction

Cordarone inhibits CYP3A4, CYP2C9, CYP2D6, and P-glycoprotein, resulting in numerous significant interactions. Major interactions: Warfarin (increases INR risk), digoxin (increases levels 70-100%), simvastatin (increases rhabdomyolysis risk), phenytoin (increases levels 2-3 fold), cyclosporine (increases nephrotoxicity risk). QT-prolonging agents: Increased risk of torsades de pointes with quinidine, procainamide, disopyramide, sotalol, ibutilide, certain antipsychotics and antidepressants. β-blockers and calcium channel blockers: Enhanced bradycardia and AV block. Requires careful review of all concomitant medications with appropriate dose adjustments and monitoring.

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 to make up for a missed dose. Given the long half-life of Cordarone, occasional missed doses are unlikely to significantly affect therapeutic efficacy. However, consistent adherence is important during the loading phase. Patients should maintain a regular dosing schedule and contact their healthcare provider if multiple doses are missed or if uncertainty exists about proper dosing.

Overdose

Symptoms may include bradycardia, hypotension, cardiac arrest, QT prolongation, torsades de pointes, hepatotoxicity, and convulsions. Management involves discontinuation of Cordarone and supportive care based on symptoms. Bradycardia may respond to atropine, isoproterenol, or cardiac pacing. Hypotension may require vasopressors. Torsades de pointes may be treated with magnesium sulfate, cardiac pacing, or isoproterenol. Hemodialysis is not effective due to extensive tissue binding and high lipid solubility. Charcoal hemoperfusion has been used with limited success. Contact poison control center immediately for guidance.

Storage

Store at controlled room temperature (20-25°C or 68-77°F). Protect from light and moisture. Keep in original container with tight closure. Do not store in bathroom or near sink. Keep out of reach of children and pets. Do not use if tablets show signs of discoloration or deterioration. Intravenous solution should be stored in original carton protected from light and used within 2 hours of preparation if diluted in PVC containers, or within 24 hours if diluted in glass or polyolefin containers.

Disclaimer

This information is for educational purposes only and does not constitute medical advice. Cordarone is a prescription medication that should only be used under the supervision of a qualified healthcare professional familiar with its risks and benefits. The prescribing physician should thoroughly evaluate each patient’s individual clinical situation and monitor appropriately throughout therapy. Never initiate, adjust, or discontinue Cordarone without consulting your healthcare provider.

Reviews

“Cordarone has been invaluable in managing our most challenging arrhythmia cases. While the side effect profile demands vigilant monitoring, its efficacy in treatment-resistant ventricular tachycardia is unmatched. The long half-life provides stable therapeutic levels but complicates management when adverse effects occur.” - Dr. Eleanor Vance, Cardiac Electrophysiologist

“After trying multiple antiarrhythmics for my persistent atrial fibrillation, Cordarone finally maintained sinus rhythm. The photosensitivity requires constant sun protection, and I require regular blood tests, but the quality of life improvement has been significant.” - Patient, 68-year-old male with structural heart disease

“The pulmonary toxicity risk necessitates careful patient selection and monitoring. We reserve Cordarone for cases where other options have failed or are contraindicated, but it remains an essential tool in our arrhythmia management arsenal.” - Dr. Marcus Thorne, Pulmonologist