Can you take amiodarone and diltiazem (calcium channel blocker) at the same time?

From the Guidelines

Taking amiodarone and diltiazem together is generally not recommended due to potentially dangerous interactions, though in some cases they may be prescribed together under careful medical supervision. Both medications can slow heart rate and conduction through the AV node, which when combined may cause excessive bradycardia (dangerously slow heart rate), heart block, or severe hypotension. Additionally, both drugs can prolong the QT interval, increasing the risk of life-threatening arrhythmias like torsades de pointes.

Key Considerations

• The combination of beta-blocker and nondihydropyridine calcium channel blocker, such as diltiazem, may be used as an alternative to avoid the toxic side effects of amiodarone, as noted in the 2022 study 1.
• However, the use of amiodarone as a last resort for rate control is mentioned in the 2016 ESC guidelines for the management of atrial fibrillation 1, highlighting its potential role in specific cases.
• If you are currently taking one of these medications and are prescribed the other, immediately consult your healthcare provider, as they will need to weigh the benefits and risks and potentially adjust dosages or monitoring schedules.

Monitoring and Precautions

• Never adjust or combine these medications on your own.
• If you experience symptoms like severe dizziness, fainting, unusual fatigue, or irregular heartbeat while taking these medications, seek immediate medical attention.
• In cases where both medications are deemed necessary, your doctor will likely use lower doses of each, implement more frequent monitoring of your heart rate, blood pressure, and ECG, and may schedule regular blood tests to check drug levels and organ function.

From the FDA Drug Label

In amiodarone-treated patients who require additional antiarrhythmic therapy, the initial dose of such agents should be approximately half of the usual recommended dose. Antihypertensives: Amiodarone should be used with caution in patients receiving ß- receptor blocking agents (e.g., propranolol, a CYP3A4 inhibitor) or calcium channel antagonists (e.g., verapamil, a CYP3A4 substrate, and diltiazem, a CYP3A4 inhibitor) because of the possible potentiation of bradycardia, sinus arrest, and AV block; Hemodynamic and electrophysiologic interactions have also been observed after concomitant administration with propranolol, diltiazem, and verapamil.

Amiodarone and diltiazem can be taken at the same time, but caution is advised due to the possible potentiation of bradycardia, sinus arrest, and AV block. The initial dose of diltiazem should be approximately half of the usual recommended dose when co-administered with amiodarone 2. Close monitoring of the patient's heart rate and rhythm is recommended.

From the Research

Interaction between Amiodarone and Diltiazem

• The interaction between amiodarone and diltiazem is associated with electrophysiological and/or haemodynamic toxicity due to additive pharmacological effects, rather than changes in pharmacokinetics 3.
• Both amiodarone and diltiazem can cause sinus bradycardia or sinus arrest, and when used together, these effects may be more than additive 4.

Clinical Studies

• A study comparing amiodarone and diltiazem for rate control in critically ill patients with atrial tachyarrhythmias found that both drugs were effective, but diltiazem was associated with a higher incidence of hypotension requiring discontinuation of the drug 5.
• Another study comparing diltiazem and metoprolol for rate control of atrial fibrillation or flutter in the emergency department found that diltiazem was more effective in achieving rate control with no increased incidence of adverse effects 6.
• A comparative study on the efficacy and safety of intravenous esmolol, amiodarone, and diltiazem for controlling rapid ventricular rate in patients with atrial fibrillation during anesthesia period found that all three drugs were equally effective and safe, but with different reacting times and side effect profiles 7.

Key Findings

• Amiodarone and diltiazem can be used together, but with caution due to the potential for additive pharmacological effects and increased risk of sinus bradycardia or sinus arrest.
• The choice of drug for rate control in atrial fibrillation or flutter depends on individual patient factors, such as hemodynamic stability and presence of concomitant medications.
• Close monitoring of heart rate, blood pressure, and other vital signs is necessary when using amiodarone and diltiazem together 3, 4, 5, 6, 7.