From the Guidelines
When combining Cardizem (diltiazem) and metoprolol, careful dosing and monitoring are essential due to their additive effects on heart rate and blood pressure, with a recommended initial dose of diltiazem 120 mg daily and metoprolol 25 mg twice daily, titrating gradually based on patient response 1. The combination of these two medications requires close monitoring of vital signs, particularly heart rate and blood pressure, as well as signs of heart failure.
- Key considerations include:
- Monitoring heart rate to maintain it above 55-60 bpm
- Regular blood pressure checks
- ECG monitoring for conduction abnormalities, such as PR interval prolongation or heart block
- Assessment for symptoms of bradycardia, hypotension, or heart failure exacerbation
- Laboratory monitoring of renal and hepatic function tests, given that both drugs are metabolized by the liver This combination therapy works through complementary mechanisms, with diltiazem blocking calcium channels and metoprolol blocking beta-adrenergic receptors, providing enhanced blood pressure control and anti-anginal effects, but with an increased risk of bradycardia and hypotension 1. Dose adjustments may be necessary in elderly patients or those with hepatic or renal impairment, and it is crucial to avoid routine use of diltiazem with beta blockers due to the increased risk of bradycardia and heart block, as noted in the 2017 ACC/AHA/AAPA/ABC/ACPM/AGS/APhA/ASH/ASPC/NMA/PCNA guideline 1.
From the FDA Drug Label
Controlled and uncontrolled domestic studies suggest that concomitant use of diltiazem hydrochloride and beta-blockers is usually well tolerated, but available data are not sufficient to predict the effects of concomitant treatment in patients with left ventricular dysfunction or cardiac conduction abnormalities Administration of diltiazem hydrochloride concomitantly with propranolol in five normal volunteers resulted in increased propranolol levels in all subjects and the bioavailability of propranolol was increased approximately 50%. If combination therapy is initiated or withdrawn in conjunction with propranolol, an adjustment in the propranolol dose may be warranted
The recommended dosing for combination therapy with Cardizem (diltiazem) and metoprolol is not explicitly stated in the FDA drug label. However, it is recommended to:
- Monitor patients closely for adverse effects
- Adjust the dose of metoprolol as needed, considering the increased bioavailability of metoprolol when co-administered with diltiazem
- Titrate the dose of diltiazem based on the patient's response to treatment 2 It is essential to exercise caution when using combination therapy, especially in patients with left ventricular dysfunction or cardiac conduction abnormalities, as the available data are not sufficient to predict the effects of concomitant treatment 2.
From the Research
Combination Therapy with Cardizem (Diltiazem) and Metoprolol
- The recommended dosing for combination therapy with Cardizem (diltiazem) and metoprolol is not explicitly stated in the provided studies, but the studies suggest that the doses of diltiazem and metoprolol can be adjusted based on the patient's response to treatment 3, 4.
- In one study, the initial dose of diltiazem was 90 mg twice daily, and the initial dose of metoprolol was 100 mg once daily 3.
- If the target blood pressure is not reached after four weeks, the doses of diltiazem and metoprolol can be doubled 3.
- The monitoring of patients on combination therapy with Cardizem (diltiazem) and metoprolol should include regular checks of blood pressure, heart rate, and electrocardiogram (ECG) 5, 6, 7.
- Patients should also be monitored for adverse effects such as hypotension, bradycardia, and tiredness 3, 4, 7.
Efficacy and Safety of Combination Therapy
- The efficacy and safety of combination therapy with Cardizem (diltiazem) and metoprolol have been evaluated in several studies 3, 5, 4, 6, 7.
- The studies suggest that both diltiazem and metoprolol can effectively lower blood pressure and heart rate in patients with hypertension or atrial fibrillation 3, 5, 6, 7.
- However, the studies also suggest that diltiazem may be more effective than metoprolol in achieving rate control in patients with atrial fibrillation 5, 6.
- The safety profiles of diltiazem and metoprolol are similar, but diltiazem may be associated with a higher risk of hypotension 7.
Specific Patient Populations
- In patients with heart failure, diltiazem may not be recommended due to its negative inotropic effects 5.
- However, one study found that intravenous diltiazem was effective and safe in patients with atrial fibrillation and heart failure 5.
- Further studies are needed to evaluate the safety and efficacy of combination therapy with Cardizem (diltiazem) and metoprolol in specific patient populations, such as those with heart failure or renal impairment.