When to Hold Amiodarone
Amiodarone should be held in patients with second- or third-degree heart block who do not have a pacemaker, in cases of bradycardia, hypotension, liver enzyme elevations greater than three times normal, and when pulmonary toxicity is suspected. 1
Cardiovascular Reasons to Hold Amiodarone
- Hold amiodarone in patients with second- or third-degree heart block who do not have a pacemaker, as it is contraindicated in these populations 1
- Discontinue or reduce infusion rate if bradycardia (occurs in 1-3% of oral therapy patients and 4.9% of IV therapy patients) or heart block develops during treatment 1, 2
- Stop infusion or reduce the rate if hypotension occurs (seen in 16% of patients receiving IV amiodarone) 1, 2
- Consider holding in patients with significant QT prolongation, as amiodarone can further prolong the QT interval (although torsades de pointes is rare with amiodarone) 1, 2
Pulmonary Reasons to Hold Amiodarone
- Immediately hold amiodarone if there are signs of pulmonary toxicity, which is the most serious non-cardiac adverse effect (occurs in 2-17% of patients) 1, 3
- Any report of worsening dyspnea or cough should prompt immediate assessment and consideration of holding amiodarone 1
- Pulmonary toxicity typically presents as subacute cough and progressive dyspnea with interstitial infiltrates on chest radiographs 1
- Routine screening for pulmonary toxicity has limited value as it can develop rapidly without prior abnormalities on chest radiographs or pulmonary function tests 1
Hepatic Reasons to Hold Amiodarone
- Hold amiodarone if liver enzyme levels are three times higher than normal, unless the patient is at high risk for recurrence of life-threatening arrhythmia 1
- Acute hepatotoxicity is rare but more common with IV amiodarone, requiring close monitoring of liver enzymes during IV administration 4
- If acute hepatitis occurs with IV amiodarone, consider not resuming oral therapy or using a lower dose (≤200 mg/day) with regular liver function monitoring 4
Other Situations Requiring Dose Adjustment or Discontinuation
- Consider holding amiodarone if thyroid dysfunction (occurs in 2-10% of patients) becomes severe and cannot be managed with appropriate therapy 1, 3
- Refer patients with changes in visual acuity or peripheral vision for ophthalmologic evaluation and consider holding the medication if optic neuropathy is confirmed 1
- Severe neurologic side effects (ataxia, peripheral neuropathy) may require dose reduction or discontinuation 1, 3
Drug Interactions Requiring Dose Adjustment
- When initiating amiodarone in patients on warfarin, reduce warfarin dose by one-third to one-half and monitor INR closely (at least weekly for first 6 weeks) 1, 5
- For patients on digoxin, reduce digoxin dose by approximately 50% when starting amiodarone, as digoxin levels typically double 1, 5
- Reduce doses of other antiarrhythmic drugs by 30-50% when co-administered with amiodarone 5
Monitoring Recommendations to Identify When to Hold Amiodarone
- Monitor liver function tests and thyroid studies every 6 months during maintenance therapy 1
- Perform chest radiograph and pulmonary function tests if pulmonary toxicity is suspected 1
- Closely monitor heart rate, especially during the first week of treatment 1
- For patients on warfarin, check prothrombin time and INR at least once weekly during the first 6 weeks of treatment 1
Special Considerations for IV Administration
- Hold or reduce the rate of IV amiodarone if heart block, bradycardia (4.9% of patients), or hypotension (16% of patients) occurs 1
- IV amiodarone should not be used in patients with bradycardia or heart block who do not have a pacemaker 1
- Higher concentrations and faster infusion rates than recommended can lead to hepatocellular necrosis and acute renal failure 5
Remember that amiodarone has a narrow therapeutic-toxic range, and the goal should be to use the minimal effective dose to reduce the risk of adverse effects while maintaining arrhythmia control 6, 3.