Amiodarone: The "New" EP Drug

Learning Advanced Cardiac Life Support (ACLS) can be a daunting task despite the new 'kinder, gentler' teaching approach. Just when you thought you had it figured out, the protocols have changed again. New medications have emerged to replace the treatments that have been standards in our profession for decades. Lidocaine is one of those 'old' standard medications. Now, it is being replaced by amiodarone in the new 2001 ACLS guidelines.

The good news is nearly everything you need to know about amiodarone is now at your fingertips in the information below, and it is relatively easy to mix and administer. Amiodarone is not a new drug, however, it may be new to some of us working in the cath lab. It is now the first-line antiarrhythmic in the recurrent VT/VF algorithm. In other words, for patients with recurrent or persistent pulseless ventricular tachycardia or ventricular fibrillation, after the three initial shocks, IV epinephrine, and another defibrillation attempt, amiodarone is the first antiarrhythmic to be considered.

The rationale for incorporating amiodarone into the ACLS protocols is supported by initial studies of the drug's use in resuscitative situations. Researchers will admit that much more investigation needs to be done but so far, early analysis looks promising. This is not only because of the drug's rapid onset of action and few adverse effects for IV use, but also because of improved outcomes. Early evidence suggests that IV amiodarone may improve survival rates for patients experiencing acute MI who received the drug during ACLS resuscitation. In addition, it has been shown that amiodarone may increase the incidence of successful defibrillation when ventricular fibrillation does not respond to epinephrine, lidocaine and multiple shocks. The most dramatic conclusions have revealed that for resuscitative measures lasting for 30 minutes or more, the percentage of patients surviving to hospital discharge was remarkably high when they received amiodarone compared to patients who had not received the drug. If all the research proves to be accurate, then amiodarone will be part of the ACLS protocols for a long time to come.

The American Heart Association dedicates a significant amount of resources testing the procedures suggested in the ACLS algorithms. We can be confident that we are doing the very best job in emergency 'code' situations when we follow the ACLS guidelines because the skills and treatments they recommend are supported by scientific research.

The following summary is designed to inform cardiac cath lab personnel about the use of amiodarone in the invasive lab setting. The side effects and adverse reactions listed below are specific to IV treatment and may be different for patients on long-term oral amiodarone therapy. It is important to remember that the underlying cause of the arrhythmia must be addressed and treated when resuscitative efforts are not productive or after the patient is stabilized.

Amiodarone (Cordorone): Class III Antiarrhythmic

Actions:

• Reduces myocardial cell membrane excitability by increasing the effective refractory period;
• Inhibits alpha and beta adrenergic stimulation; causing peripheral vasodilation and decreased heart rate.

Uses:

• Cardiac arrest due to life-threatening and recurrent ventricular arrhythmias;
• Prophylactic treatment of recurrent ventricular fibrillation and ventricular tachycardia;
• Treatment of supraventricular tachycardia;
• Preliminary treatment of hemodynamically stable, wide complex tachycardia;
• May be used to control ventricular rate in atrial fibrillation.
•  

Contraindications:

• No contraindications for use in cardiac arrest;
• Cardiogenic shock;
• Sick sinus syndrome, sinus bradycardia, second- and third-degree AV block (unless patient has a functioning pacemaker);
• Electrolyte imbalance;
• Pregnant or nursing mothers (pregnancy category C); amiodarone crosses the placenta and enters breast milk;
• For long-term oral therapy: use with caution in patients with a history of congestive heart failure, severe pulmonary disease (can cause adult respiratory distress syndrome (ARDS) and pulmonary fibrosis, hepatic disease (metabolized by the liver), and thyroid disorders (can cause hypothyroidism).

Dose and Administration:

• Cardiac arrest: 300 mg rapid IV push, may repeat 150 mg IV push in 3–5 minutes if needed;
• Wide complex tachycardia: (when blood pressure is stable) 150 mg IV over 10 minutes (15 mg/minute), this dose may be repeated every 10 minutes as necessary, or 360 mg IV over 6 hours (1 mg/minute);
• Maintenance infusion: 0.5 mg/minute (540 mg over 18 hours);
• Maximum dose: 2.2 grams IV over 24 hours;
• To administer: use a large bore needle and draw up slowly to prevent foaming. Mix 2 amps in 20–30 ml of D5W, do not shake solution;
• How supplied: 50 mg/ml.

Adverse Reactions:

• Hypotension, bradycardia, CHF, sinus arrest;
• Long-term PO use: pulmonary fibrosis, Adult Respiratory Distress Syndrome (ARDS).

Side Effects:

• Headache, dizziness, nausea, vomiting;
• Liver function abnormalities;
• Hypothyroidism, although this side effect is minimal for short-term IV treatment.

Special Considerations:

• May cause negative inotropic effects;
• Do not use routinely with other drugs that prolong QT interval (i.e., procainamide);
• Rapid onset of action when administered IV;
• Amiodarone cannot be removed from the body with dialysis: it is metabolized in the liver and eliminated by biliary excretion;
• Drug interactions: increases the anticoagulant effects of coumadin; increases blood levels of digoxin, quinidine, procainamide, mexiletine, flecainide (Tambocor), disopyramide (Norpace), phenytoin (Dilantin), lidocaine;
• Monitor ECG during administration: report prolonged QT intervals, or bradycardia;
• For patients on long-term amiodarone therapy: monitor respiratory status and report tachypnea, dyspnea, rales/crackles;
• Do not confuse amiodarone (Cordorone) with amrinone (Inocor).

For more information about pharmaceuticals, check out the Cardiac Catheterization Medications Guide by Leslie Yaniga, which was reviewed in the May 2001 Cath Lab Digest. To order, contact SmithNotes at tel. (941) 910-4290 or send check or PO# for $60.00 (includes shipping and handling), to SmithNotes, P.O. Box 152116, Cape Coral, FL 33915-2116.