From the Guidelines
Amiodarone and metoprolol tartrate can be taken together, but this combination requires careful medical supervision due to potential interactions, as highlighted in the 2022 European Heart Journal review 1. When considering the combination of these two medications, it's crucial to understand their individual effects on the heart and potential interactions. Amiodarone, an antiarrhythmic drug, can increase the risk of bradycardia and hypotension, while metoprolol tartrate, a beta-blocker, can also slow the heart rate and lower blood pressure.
- Key considerations for their combined use include:
- Monitoring for symptoms of excessive bradycardia or hypotension, such as dizziness, unusual fatigue, shortness of breath, or feeling faint.
- Potential for amiodarone to increase blood levels of metoprolol by affecting its liver metabolism, thereby enhancing its effects.
- The need for careful dosage adjustment of both medications under medical supervision to minimize adverse effects. According to the 2014 AHA/ACC/HRS guideline for the management of patients with atrial fibrillation 1, metoprolol tartrate can be used with careful consideration of its dosing, starting at 25–100 mg BID, and amiodarone's dosing should be maximized at 200 mg/day for maintenance.
- It is essential to follow the recommendations from the highest quality and most recent study, which in this case is the 2022 review from the European Heart Journal 1, emphasizing cautious use and monitoring when combining these medications.
From the FDA Drug Label
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; if necessary, amiodarone can continue to be used after insertion of a pacemaker in patients with severe bradycardia or sinus arrest
The use of amiodarone with metoprolol (a ß-receptor blocking agent) may require caution due to the potential for bradycardia, sinus arrest, and AV block. It is recommended to use amiodarone with caution in patients receiving ß-receptor blocking agents, such as metoprolol. Monitoring for adverse effects, especially conduction disturbances, is necessary when combining these medications 2.
From the Research
Safety of Taking Amiodarone and Metoprolol Together
- The combination of amiodarone and metoprolol may increase the risk of bradycardia and atrioventricular block due to the inhibition of cytochrome P450 (CYP) 2D6 by amiodarone, leading to increased metoprolol concentrations 3.
- A study found that amiodarone use was associated with higher metoprolol concentrations and lower heart rates in patients taking metoprolol 3.
- Another study investigated the use of metoprolol and amiodarone in combination for prophylaxis against atrial fibrillation after cardiac surgery, and found that the combination was associated with a high incidence of side effects, especially bradycardia 4.
- An experimental study in isolated perfused rat hearts found that the combination of metoprolol and amiodarone had a negative chronotropic effect, but did not depress myocardial contractility or accentuate bradycardia compared to metoprolol alone 5.
- A prospective study found that the addition of metoprolol to amiodarone therapy was effective in controlling refractory ventricular tachycardia, but caused hemodynamic deterioration in some patients 6.
- A pharmacokinetic study found that amiodarone increased the serum concentration/dose ratio of metoprolol in patients with cardiac arrhythmia, suggesting a significant interaction between the two drugs via inhibition of CYP2D6 7.
Key Findings
- Increased risk of bradycardia and atrioventricular block due to increased metoprolol concentrations 3, 4.
- High incidence of side effects, especially bradycardia, with combination therapy 4.
- Negative chronotropic effect without depressing myocardial contractility or accentuating bradycardia in experimental study 5.
- Effective in controlling refractory ventricular tachycardia, but with potential for hemodynamic deterioration 6.
- Significant pharmacokinetic interaction between amiodarone and metoprolol via inhibition of CYP2D6 7.