ACLS Drugs – Amiodarone
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Article at a Glance
- Amiodarone is a Class 3 potassium channel inhibitor antiarrhythmic.
- It is indicated for ventricular arrhythmias.
- Initial dose for pVT and VF = 300 mg IVP.
- Initial dose for VT with a pulse = 150 mg IVP over 10 minutes.
- Side effects include bradycardia and hypotension.
Antiarrhythmic Classifications
While amiodarone is classified as an antiarrhythmic used to treat ventricular fibrillation (VF), what does it actually do?
Antiarrhythmics are classified based on their mechanism of action, specifically how they impact cells’ cardiac action potential. There are several antiarrhythmic classifications: Class I, Class II, Class III, Class IV, and Class V.
- Class I antiarrhythmics are sodium channel blockers, such as lidocaine.
- Class II antiarrhythmics are beta-blockers, such as metoprolol, and most drugs ending in -lol. Most drugs ending in -lol are beta-blockers but not all of them.
- Class III antiarrhythmics are potassium channel blockers. Amiodarone is primarily, but not exclusively, a potassium channel blocker.
- Class IV antiarrhythmics are calcium channel blockers, such as verapamil and diltiazem.
- Class V antiarrhythmics are miscellaneous antiarrhythmics, such as adenosine and atropine. They don’t really fit in any other category.
Related Video – Cardiac Conduction & Action Potentials
Antiarrhythmic Classification of Amiodarone
Amiodarone is a complex drug. It is classified as a Class III potassium channel inhibitor, though it contains other elements. It has calcium channel blocker properties, beta-blocker properties, and sodium channel blocker properties. It impacts a lot of the cardiac cells’ action potential and is a very complex drug.
All antiarrhythmics suppress cardiac cell and heart function. Therefore, all antiarrhythmics can cause bradycardia and hypotension. When you’re looking at the drug’s exact mechanism of action, you can anticipate the drug’s effects and negative side effects.
Indications and Dosing in ACLS
Per the International Liaison Committee on Resuscitation (ILCOR) and American Heart Association (AHA) recommendations, we use amiodarone for ventricular arrhythmias such as ventricular tachycardia (VT) and ventricular fibrillation (VF).
Related Video – ECG Rhythm Review – Ventricular Fibrillation
Related Video – ECG Rhythm Review – Ventricular Tachycardia
In ACLS, amiodarone treats ventricular arrhythmias.
For pulseless VT and ventricular fibrillation, the initial amiodarone dose is a 300 mg IV push. Amiodarone often comes supplied as 150 mg in 3mL, so you’ll need two vials and at least a 6 mL syringe.
Read: ACLS Drugs – Adenosine
Physicians need two 150 mg vials to administer 300 mg of amiodarone.
Remember, pulseless ventricular tachycardia and ventricular fibrillation are treated the same way.
You can also use amiodarone to treat stable ventricular tachycardia. In this case, stability refers to hemodynamic stability.
Related Video – Hemodynamics – Part 1
Related Video – Hemodynamics – Part 2
Remember this rule: don’t just treat rhythms. Treat the patients that have rhythms, with the exception of VT. VT is treated regardless of whether the patient is stable or unstable because unrecognized or untreated VT will ultimately deteriorate into ventricular fibrillation (VF).
The dosing for hemodynamically stable VT is 150mg over 10 minutes. How is it administered? Always follow local protocols. Protocols usually suggest taking 150 milligrams of amiodarone in a 3mL vial, injecting the drug into a 100 mL bag of a D5W, and spiking it with 60-drop tubing before administering the amiodarone over 10 minutes.
In the field, use 150mg/3mL amiodarone, 100mL D5W, and a 60-drop tubing for a stable VT.
Always use 60 drop tubing to ensure that you don’t inject the drug directly into the patient. To calculate drip rates, if you have a 100 mL bag of D5W with 60 drop tubing over 10 minutes, the drip rate is 600 drops per minute.
If you’re in the field, it’s impossible to count, so there’s another technique. Remember with any technique to follow your protocols.
Amiodarone’s drip rate is 600 drops per minute.
If you start the amiodarone drip with a 60 drop tube, you’ll see a stream. Throttle that back using your roller clamp until you see drips forming around the 10-minute mark. Experiment with it. Get a bag of 100 mL D5W and 60 drop tubing and time it. You’ll see it’s close to 10 minutes. If you’re in the field without an IV pump, that’s as close as you’ll get.
Another possible method is using a 10 mL syringe of normal saline. Waste 3 mL of saline, draw up 3mL of 150mg/3mL of amiodarone, and administer 1mL per minute.
Other Considerations
Remember that all antiarrhythmics suppress cardiac function, yet they all operate a little differently and have different half-lives. For example, lidocaine’s half-life is 1.5–2 hours. In comparison, amiodarone’s half-life is around 40 days. Again, they all cause cardiac suppression. Physicians must be alert for changes in a patient’s mental status, blood pressure, potential bradycardic development, and any other changes detected while monitoring and reassessing the patient.
Summary
Amiodarone is a Class III antiarrhythmic used to treat VF. It’s primarily a potassium channel blocker, though it contains other elements. Antiarrhythmics suppress cardiac cell and heart function, and they all have vastly different half-lives. Physicians should make sure to administer these drugs properly.
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Editorial Note
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