Cardiovascular Pharmacotherapy

Introduction to Calcium Channel Blockers

Calcium channel blockers should be used with caution in certain patient populations, such as those with heart failure with reduced ejection fraction (HFrEF), and avoided with beta blockers due to increased risk of bradycardia and heart block, as noted by the American Heart Association/American College of Cardiology guidelines 1, 2

Calcium channel blockers, such as diltiazem, are effective for management of supraventricular tachycardia, with evidence supporting its effectiveness, and can be used for rate control in atrial fibrillation, as recommended by the American College of Cardiology 3, 4
Diltiazem is effective for symptomatic management of AVNRT when catheter ablation is not an option, according to the American Heart Association 3
Amlodipine is preferred for vasospastic angina, with a daily dose of 5-10mg, while diltiazem (120-360mg daily) is preferred for rate control plus hypertension, as recommended by the American College of Cardiology 5

The American Heart Association/American College of Cardiology guidelines recommend avoiding the use of calcium channel blockers, such as diltiazem and verapamil, in patients with systolic heart failure, and the use of calcium channel blockers in combination with beta-blockers for hypertrophic cardiomyopathy is unsupported by evidence 6, 3
Patients with pre-existing bradycardia, AV block, sick sinus syndrome, heart failure with reduced ejection fraction (HFrEF), or hypotension should avoid concurrent use of amlodipine and diltiazem, due to increased risk of additive hypotension, bradycardia, and conduction disturbances 7, 5

Diltiazem affects AV nodal conduction, which can be exacerbated when combined with amlodipine, a dihydropyridine calcium channel blocker, and is a moderate inhibitor of CYP3A4, which can affect the metabolism of amlodipine, potentially increasing amlodipine concentrations and side effects 7, 5
Amlodipine is a dihydropyridine CCB that primarily affects peripheral vasculature with minimal cardiac effects, whereas diltiazem is a non-dihydropyridine CCB that significantly affects cardiac conduction and contractility 5
If concurrent use of amlodipine and diltiazem is necessary, monitoring of blood pressure and heart rate should be done frequently, with baseline ECG and regular assessments for conduction abnormalities, starting with the lowest possible doses of both medications, and amlodipine can be dosed once daily (2.5-10mg), while diltiazem often requires multiple daily dosing unless using extended-release formulations 5
If additional antihypertensive therapy is needed beyond a single CCB, the preferred approach is to choose a medication from a different class, such as an ACE inhibitor or ARB, thiazide diuretic, or beta-blocker (if indicated for compelling conditions like CAD) 5