Focus on Pharm: Amiodarone

Amiodarone is a common medication you’ll see used both acutely in the clinical setting and chronically for outpatient therapy. We’ll go through Amiodarone using the Straight A Nursing DRRUGS framework. 

D: Drug Class

Amiodarone is in the therapeutic class of antiarrhythmics, specifically class III antiarrhythmics which are further classified as potassium-channel blockers. These medications work by altering membrane ion conduction, which then alters cardiac action potentials. 

Recall that the potassium channels play a key role in repolarization. When we block these channels, we delay repolarization and increase the effective refractory period. The result is that we suppress reentry tachycardias. Note that this will also prolong the QT interval, so if you want to learn more about that, then take a quick detour here.

R: Routes

Amiodarone can be given via an IV infusion or a tablet. How we typically utilize amiodarone in the clinical setting is that patients are started on an IV infusion and then transitioned to PO medication if they will be taking it long term. 

R: Regular Dose Range

The dose of amiodarone will depend on the formulation and what it is being used for.

For ventricular arrhythmias, we can give amiodarone PO or IV. The dose for PO amiodarone will start high and then taper down to a maintenance dose. The starting dose is between 800 to 1600 mg per day in one or two divided doses for one to three weeks. It is then decreased to 600 to 800 given in 1 or 2 daily divided doses for approximately one month. It is then further decreased to a maintenance dose of 400 mg/day. 

The IV form of amiodarone is first given as a bolus of 150 mg over 10 minutes. We then follow with 360 mg given over the next 6 hours (1 mg/min), and then 540 mg over the next 18 hours (0.5 mg/min). Some patients will stay on this dose of 0.5 mg/min until they are fully transitioned to oral therapy.

Amiodarone is also sometimes used in ACLS for pulseless ventricular tachycardia and ventricular fibrillation. The dose for this use is 300 mg IV push that may be followed with one 150 mg dose after 3 to 5 minutes. There is a max dose of 2.2 grams in 24 hours, so if your patient is coding multiple times, you’ll want to keep track of how much amiodarone they have received.

For supraventricular tachycardias, patients are usually administered PO amiodarone with the adult dose being 600-800 mg/day for one week or until the desired response is seen. The dose is then decreased to 400 mg/day for about three weeks, followed by a maintenance dose of 200-400 mg/day.

In general, most patients will be on a dose somewhere between 200 to 400 mg per day, unless they have just started therapy.

U: Uses

It’s always important to understand why YOUR patient is taking any medication, especially medications that are used for multiple purposes. 

Amiodarone is used to treat ventricular tachycardia (with or without a pulse), ventricular fibrillation, and supraventricular tachyarrhythmias (namely atrial fibrillation and atrial flutter.)

G: Guidelines

Amiodarone is a highly potent medication that comes with a lot of monitoring parameters and safety guidelines. 

• Amiodarone is a “BEERS drug.” For more information, learn about the BEERS list here.
• Because this medication affects conduction, it is avoided in patients with conduction defects…namely 2nd and 3rd degree AV block. It is also avoided in patients with bradycardia who do not have a pacemaker.
• Amiodarone has a lot of drug-drug interactions. The key ones to know are that it will cause increased levels of digoxin and class I antiarrhythmics such as lidocaine. It will also increase theophylline levels as well as phenytoin, cyclosporine and carvedilol. 
• Another key drug interaction to know is warfarin – amiodarone will increase the activity of warfarin, so dose adjustments will likely need to be made to decrease bleeding risk.
• Patients taking amiodarone should not drink grapefruit juice because it inhibits enzymes in the GI tract that metabolize the medication, leading to increased levels and risk for toxicity.
• You’ll want to monitor the EKG continuously during IV amiodarone infusion and initiation of PO therapy.
• Amiodarone can cause pulmonary toxicity and ARDS, so monitor your patient’s respiratory status carefully. Patients taking amiodarone long-term should get regular chest x-rays and pulmonary function tests.
• Due to its high iodine content (about 37%), amiodarone can cause thyroid dysfunction, so monitor your patient for signs of hypothyroidism as well as hyperthyroidism.
• The labs you’ll monitor for a patient taking amiodarone are the liver function tests…AST, ALT and alkaline phosphatase. You’ll also monitor your patient’s calcium, magnesium and potassium levels as deficiencies in these can decrease effectiveness of the medication. 
• IV amiodarone is administered through an inline filter. You can learn more about safe IV medication administration here.
• Key teachings for your patient are to monitor pulse daily, avoid grapefruit juice and that side effects can appear up to a year after initiation of therapy. 
• Teach your patient that the effects of amiodarone can persist for months after discontinuation, due to the drugs long half life of up to 100 days.

S: Side Effects

Amiodarone has a pretty significant side effect profile that can affect many organ systems. This includes the eyes, endocrine system, GI tract, cardiovascular system and neurological system. These common side effects include: 

• Corneal microdeposits
• Nausea/vomiting, constipation, anorexia
• Ataxia, involuntary movements, peripheral neuropathy, dizziness, and fatigue
• Hypotension and bradycardia
• Photosensitivity (even through glass and thin clothing or with use of sunscreen)
• Hypothyroidism (hyperthyroidism can occur, but isn’t as common)

The most serious side effects are cardiac, pulmonary and dermatologic in nature. 

• Pulmonary fibrosis, acute respiratory distress syndrome (ARDS), pulmonary toxicity
• Prolongation of the QT interval (which can lead to ventricular fibrillation or torsades de pointes, both of which are lethal ventricular rhythms), worsening of arrhythmias and heart failure
• Toxic epidermal necrolysis (though this is rare)
• And though this is rare, it seems like the sort of thing that would show up on a nursing school exam… a bluish discoloration to the skin of the arms, face and neck can occur after prolonged use.

So there you have it, your quick introduction to Amiodarone. Want an even quicker overview? Here are the absolute MOST IMPORTANT things to know about Amiodarone: 

• Amiodarone is a treatment for supraventricular and ventricular tachyarrhythmias
• Comes in PO or IV form
• If given IV, use an inline filter
• There are many drug-drug interactions, and patients should avoid grapefruit juice
• Side effects can be significant and involve multiple organs
• Patients should be on continuous EKG monitoring during IV infusions and initiation of oral therapy

Interested in more cardiac topics? Simply type “cardiac” in the search bar above and all my blog posts and podcast episodes tagged with “cardiac” will magically appear.

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References:

Colunga Biancatelli, R. M., Congedo, V., Calvosa, L., Ciacciarelli, M., Polidoro, A., & Iuliano, L. (2019). Adverse reactions of Amiodarone. Journal of Geriatric Cardiology : JGC, 16(7), 552–566. https://doi.org/10.11909/j.issn.1671-5411.2019.07.004

Klabunde, R. E. (2007, March 14). Antiarrhythmic drugs. Cardiovascular Pharmacology Concepts. https://www.cvpharmacology.com/antiarrhy/antiarrhythmic

Klabunde, R. E. (2011, December 21). Potassium-channel blockers. Cardiovascular Pharmacology Concepts. https://www.cvpharmacology.com/antiarrhy/potassium-blockers

Narayana, S. K., Woods, D. R., & Boos, C. J. (2011). Management of amiodarone-related thyroid problems. Therapeutic Advances in Endocrinology and Metabolism, 2(3), 115–126. https://doi.org/10.1177/2042018811398516