From the Guidelines
No, you should not combine nifedipine and diltiazem as they are both calcium channel blockers and taking them together increases the risk of serious side effects. This combination can cause excessive blood pressure lowering, which may lead to dizziness, fainting, or inadequate blood flow to vital organs. Additionally, both medications slow heart rate and cardiac conduction, potentially causing dangerous heart rhythm problems or heart failure when used together. The combination can also increase the blood levels of either medication due to competition for the same metabolic pathways in the liver, leading to toxicity. According to the 2012 ACCF/AHA focused update incorporated into the ACCF/AHA 2007 guidelines for the management of patients with unstable angina/non-st-elevation myocardial infarction 1, calcium channel blockers may be used to control ongoing or recurring ischemia-related symptoms in patients who already are receiving adequate doses of nitrates and beta blockers. However, rapid-release, short-acting dihydropyridines (eg, nifedipine) must be avoided in the absence of concomitant beta blockade because of increased adverse potential.
Key Considerations
- The combination of nifedipine and diltiazem can lead to excessive blood pressure lowering and increased risk of heart rhythm problems or heart failure.
- The use of calcium channel blockers in patients with unstable angina/non-st-elevation myocardial infarction should be guided by the patient's individual clinical profile and the presence of other medications, such as beta blockers.
- Alternative treatment options, such as adding a medication from a different class (e.g., ACE inhibitor, ARB, or beta-blocker), may be safer and more effective in cases where blood pressure or angina remains poorly controlled on a single calcium channel blocker.
Evidence-Based Recommendations
The evidence from the 2012 ACCF/AHA focused update incorporated into the ACCF/AHA 2007 guidelines for the management of patients with unstable angina/non-st-elevation myocardial infarction 1, 2, 3 suggests that the combination of nifedipine and diltiazem should be avoided due to the increased risk of serious side effects. Instead, healthcare providers should consider alternative treatment options that take into account the patient's individual clinical profile and the presence of other medications.
From the FDA Drug Label
Diltiazem: Pre-treatment of healthy volunteers with 30 mg or 90 mg t. i.d. diltiazem p.o. increased the AUC of nifedipine after a single dose of 20 mg nifedipine by factors of 2.2 and 3.1, respectively. The corresponding Cmax values of nifedipine increased by factors of 2.0 and 1. 7, respectively. Caution should be exercised when co-administering diltiazem and nifedipine and a reduction of the dose of nifedipine should be considered.
Combination of nifedipine and diltiazem is possible, but caution is advised due to increased exposure to nifedipine. A reduction of the dose of nifedipine should be considered when co-administering with diltiazem 4. Monitoring of blood pressure is recommended to avoid potential hypotensive effects.
From the Research
Combination Therapy with Nifedipine and Diltiazem
- The combination of nifedipine and diltiazem has been studied in patients with severe hypertension and stable angina pectoris 5, 6.
- Laboratory investigations have shown a synergistic effect on receptor binding, as well as increased drug levels with the concurrent use of diltiazem and a dihydropyridine calcium channel blocker (nifedipine or nicardipine) 5.
- A study found that combination therapy with nifedipine and diltiazem was more effective in patients who did not maximally respond to diltiazem or nifedipine alone, with respect to anginal and exercise variables and in reducing blood pressure at rest and during exercise 6.
- However, combination therapy was also associated with more side effects, and diltiazem may increase nifedipine drug levels when the drugs are combined 6.
Safety and Efficacy
- Diltiazem is generally well-tolerated, but it can cause atrioventricular block, which may be exacerbated by concomitant beta-adrenoceptor antagonist therapy 7, 8.
- Nifedipine and diltiazem have been shown to be effective in reducing angina and improving exercise tolerance, but their combination may increase the risk of adverse effects 6.
- Patients on combination therapy should be closely monitored for adverse effects, including blood pressure, heart rate, and atrioventricular conduction on ECG 7.
Clinical Use
- The combination of nifedipine and diltiazem may be useful in patients with severe hypertension or stable angina pectoris who do not respond to monotherapy 5, 6.
- However, the decision to use combination therapy should be made on a case-by-case basis, taking into account the individual patient's risk factors and medical history 7, 8.