Amlodipine vs Diltiazem

Both amlodipine and diltiazem effectively lower blood pressure. Amlodipine is a potent vasodilator and is among the most commonly prescribed antihypertensive medications. The ALLHAT trial (the largest antihypertensive trial ever conducted) included amlodipine and demonstrated its efficacy in reducing cardiovascular events.

Diltiazem lowers blood pressure through vasodilation and also reduces heart rate and cardiac conduction. This dual action makes diltiazem particularly useful for patients with both hypertension and rapid atrial fibrillation or supraventricular tachycardia.

For angina, both drugs are effective, but diltiazem also reduces myocardial oxygen demand by slowing heart rate, providing benefit through two mechanisms. Amlodipine is preferred in combination with beta-blockers for angina since diltiazem combined with beta-blockers can cause excessive bradycardia.

Peripheral edema: Amlodipine frequently causes ankle and leg swelling (dose-dependent, occurring in up to 10-15% of patients at higher doses) due to precapillary vasodilation. Diltiazem causes significantly less peripheral edema because it also dilates postcapillary venules, reducing the pressure gradient.

Heart rate: Amlodipine does not significantly affect heart rate and may cause mild reflex tachycardia. Diltiazem slows heart rate and can cause bradycardia, particularly in combination with other rate-lowering drugs.

Constipation: Diltiazem (and especially verapamil, another non-DHP CCB) can cause constipation. This is less common with amlodipine.

Drug interactions: Diltiazem is a moderate CYP3A4 inhibitor and can increase levels of many drugs including statins (particularly simvastatin), cyclosporine, and certain benzodiazepines. Amlodipine has fewer drug interactions.

Both drugs may cause headache, dizziness, and flushing, though these are more common with amlodipine.

Both amlodipine and diltiazem are available as inexpensive generics. A 30-day supply of either drug typically costs $4-$20 at most pharmacies. Extended-release formulations of diltiazem may cost slightly more depending on the brand.

Both are covered by virtually all insurance plans. Cost differences are generally minimal.

Amlodipine is taken once daily (half-life of 30-50 hours), making it one of the simplest antihypertensives to take. It does not need to be taken with food.

Diltiazem's dosing depends on the formulation: immediate-release requires 3-4 times daily dosing, while extended-release formulations (Cardizem CD, Tiazac, Dilacor XR) allow once- or twice-daily dosing. The variety of diltiazem ER formulations can be confusing, as they are not all interchangeable.

Amlodipine has a clear convenience advantage due to its simple once-daily dosing with a single formulation.

Amlodipine is generally preferred as a first-line antihypertensive due to its once-daily dosing, strong trial evidence (ALLHAT), and compatibility with beta-blockers. It is the better choice when blood pressure is the primary concern and when combination therapy with a beta-blocker is needed.

Diltiazem is preferred when heart rate control is also needed (atrial fibrillation, SVT), for patients who cannot tolerate beta-blockers, or for patients who develop significant ankle edema on amlodipine. It should be used cautiously with beta-blockers due to additive bradycardia risk.

Neither drug should be used in patients with heart failure with reduced ejection fraction (HFrEF), though amlodipine has some safety data in this population (PRAISE trial). Consult your healthcare provider for individualized recommendations.