Can a patient be on both amlodipine and diltiazem?

Concurrent Use of Amlodipine and Diltiazem

Patients should not be on both amlodipine and diltiazem concurrently due to the increased risk of additive hypotension, bradycardia, and conduction disturbances that could lead to significant cardiovascular complications. 1

Pharmacological Rationale Against Concurrent Use

Amlodipine and diltiazem belong to different subclasses of calcium channel blockers (CCBs) with overlapping but distinct mechanisms:

• Amlodipine: Dihydropyridine CCB that primarily affects peripheral vasculature with minimal cardiac effects 2, 1
• Diltiazem: Non-dihydropyridine CCB that significantly affects cardiac conduction and contractility 2, 1

When used together, these medications can cause:

1. Additive hypotension: Both medications lower blood pressure, and combined use increases risk of symptomatic hypotension 1
2. Conduction abnormalities: Diltiazem affects AV nodal conduction, which can be exacerbated when combined with amlodipine 2
3. Pharmacokinetic interactions: Diltiazem is a moderate CYP3A4 inhibitor that can increase amlodipine concentrations by up to 60% 3

Guideline Recommendations

Multiple guidelines specifically advise against routine concurrent use:

• The American Heart Association/American College of Cardiology guidelines note: "Avoid routine use with beta blockers because of increased risk of bradycardia and heart block. Do not use in patients with HFrEF." 2

• Guidelines for hypertrophic cardiomyopathy state: "The use of calcium channel blockers in combination with beta-blockers, as therapy directed at HCM, is unsupported by evidence" 2

Clinical Scenarios Where Each Drug Is Preferred

Amlodipine Preferred:

• Hypertension requiring once-daily dosing 2
• Patients with stable angina pectoris 4
• Elderly patients or those with hepatic insufficiency (with dose adjustment) 3

Diltiazem Preferred:

• Management of supraventricular tachycardia 2
• Rate control in atrial fibrillation 2
• Symptomatic management of AVNRT when catheter ablation is not an option 2

Alternative Approaches

If additional antihypertensive therapy is needed beyond a single CCB:

• Choose a medication from a different class (ACE inhibitor, ARB, thiazide diuretic) 1
• For patients requiring both vasodilation and rate control, consider alternative combinations with fewer interactions 1

Special Considerations

• Heart Failure: Both diltiazem and verapamil should be avoided in patients with systolic heart failure 2
• Drug Interactions: Amlodipine co-administered with 180 mg daily dose of diltiazem resulted in a 60% increase in amlodipine systemic exposure 3
• Persistence of Effect: Amlodipine has a longer half-life (30-50 hours) compared to diltiazem, providing better coverage during missed doses 3, 5

In exceptional circumstances where no alternative exists and both medications must be used, start with the lowest possible doses of both medications with frequent monitoring of blood pressure, heart rate, and ECG for conduction abnormalities 1.