amiodarone, Cordarone (cont.)

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Medical and Pharmacy Editor:

 Ritonavir (Norvir) can inhibit the enzyme that is responsible for the metabolism (break-down) of amiodarone. Although no clinical problems have been recognized as a result of this interaction, it would be prudent to avoid this combination for fear of the potential for amiodarone toxicity.

Amiodarone also can interact with tricyclic antidepressants (for example, amitriptyline [Endep, Elavil]), or phenothiazines (for example, chlorpromazine [Thorazine]) and potentially cause serious arrhythmias.

Amiodarone interacts with warfarin (Coumadin) and increases the risk of bleeding. The bleeding can be serious or even fatal. This effect can occur as early as 4-6 days after the start of the combination of drugs or can be delayed by a few weeks. Clotting studies probably should be done early during treatment with amiodarone among patients taking warfarin.

Amiodarone can interact with some cholesterol-lowering medicines of the statin class, such as simvastatin (Zocor), atorvastatin (Lipitor), and lovastatin (Mevacor), increasing the side effects of statins which include severe muscle breakdown, kidney failure or liver disease. This interaction is dose-related, meaning that lower doses of statins are safer than higher doses when used with amiodarone. An alternative statin, pravastatin (Pravachol), does not share this interaction and is safer in patients taking amiodarone.

Amiodarone inhibits the metabolism of dextromethorphan, the cough suppressant found in most over-the-counter (and some prescription) cough and cold medications (for example, Robitussin-DM). Although the significance of the interaction is unknown, these two drugs probably should not be taken together if possible.

Grapefruit juice may reduce the breakdown of amiodarone in the stomach leading to increased amiodarone blood levels. Grapefruit juice should be avoided during treatment with amiodarone.

PREGNANCY: Amiodarone should not be used during pregnancy because it can cause fetal harm. There have been reports of congenital hypothyroidism or hyperthyroidism when amiodarone was administered during pregnancy.

NURSING MOTHERS: Amiodarone is excreted in breast milk and may cause adverse effects in the infant. Breastfeeding should be discontinued by mothers receiving amiodarone.

SIDE EFFECTS: Amiodarone has many side effects and several that are serious. This is only a partial list. Common side effects include fatigue, eye deposits, tremor, unsteady gait, nausea, vomiting, constipation, weight loss, dizziness, and visual changes. Amiodarone is also associated with heart block, low blood pressure, pulmonary fibrosis (scarring of the lungs), heart failure, cardiac arrest, hypo or hyperthyroidism, blue skin discoloration, liver failure, and cardiogenic shock.

Reference: FDA Prescribing Information

Last Editorial Review: 1/4/2012

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