amiodarone

Amiodarone has many side effects, some severe and potentially fatal, but it has successfully treated arrhythmias when other drugs have failed. It is a "broad spectrum" antiarrhythmic medication that has complex effects on the heart’s electrical activity. Its important electrical effects include:

1. a delay in heart’s electrical system "recharges" after contraction (repolarization);
2. prolongation in the electrical phase during which the heart’s muscle cells are stimulated (action potential);
3. a slowing of the speed of electrical conduction through the heart’s electrical system;
4. a reduction in the firing of the heart’s pacemaker;
5. a slowing of conduction through specialized electrical pathways responsible for arrhythmias.

Amiodarone also dilates blood vessels, which can benefit patients with congestive heart failure.

Amiodarone was discovered in 1961 and FDA approved in December 1985.

Warnings

• Cordarone is intended for use only in patients with life-threatening arrhythmias due to substantial toxicity.
• Cordarone can cause potentially fatal toxicities, especially pulmonary toxicity. Pulmonary toxicity has been fatal in about 10% of cases.
• Liver injury is common with Cordarone, but usually mild. Overt liver disease can occur and has been fatal in a few cases.
• Cordarone can exacerbate arrhythmias, making them less well tolerated or more difficult to reverse. This occurs in 2 to 5% of patients and can cause significant heart block or sinus bradycardia.

Side effects of amiodarone

Common side effects of amiodarone include:

• heart block,
• low blood pressure,
• pulmonary fibrosis (scarring of the lungs),
• heart failure,
• cardiac arrest,
• hypothyroidism or hyperthyroidism,
• blue skin discoloration,
• liver failure,
• cardiogenic shock.

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Dosage for amiodarone

• The recommended dosing schedule is an initial loading dose of 800-1600 mg daily for 1 to 3 weeks, followed by 600-800 mg daily for 1 month, then 400 mg daily for maintenance.
• The response should be closely monitored, and dosing is individualized for each patient.
• Amiodarone may be administered once daily or given twice daily with meals to minimize stomach upset seen more frequently with higher doses.

Drug interactions with amiodarone

• Amiodarone may interact with beta-blockers and calcium channel blockers, resulting in an excessively slow heart rate or a block in the conduction of the electrical impulse through the heart.
• Amiodarone increases the blood levels of digoxin. The dose of digoxin should be reduced by 50% when amiodarone therapy is started.
• Amiodarone increases blood concentrations of flecainide, procainamide, and quinidine.
• Ritonavir, tipranavir, indinavir, and saquinavir should not be combined with amiodarone.
• Amiodarone can interact with tricyclic antidepressants or phenothiazines and potentially cause serious arrhythmias.
• Amiodarone interacts with warfarin and increases the risk of bleeding.
• Amiodarone can interact with some cholesterol-lowering medicines and increase the side effects.
• Amiodarone inhibits the metabolism of dextromethorphan, the cough suppressant found in most over-the-counter cough and cold medications.
• Grapefruit juice may reduce the breakdown of amiodarone in the stomach, leading to increased amiodarone blood levels. It should be avoided during treatment with amiodarone.

Safety of amiodarone during pregnancy and breastfeeding

• Amiodarone should not be used during pregnancy because it can cause fetal harm.
• Amiodarone is excreted in breast milk and may cause adverse effects in the infant. Breastfeeding should be discontinued by mothers receiving amiodarone.

Other important information about amiodarone

Available preparations of amiodarone:

• Tablets: 100, 200 mg. Injection: 50 mg/ml., 1.5 g/ml., 1.8 g/ml.

Storage of amiodarone:

• Tablets and injections should be kept at room temperature, 20 C to 25 C (68 F to 77 F).

Summary

Amiodarone is prescribed to correct abnormal heart rhythms. It has potentially fatal toxicities, including pulmonary toxicity. Common side effects of amiodarone include fatigue, eye deposits, tremor, unsteady gait, nausea, vomiting, constipation, weight loss, dizziness, and visual changes.