Can diltiazem (calcium channel blocker) lower blood pressure?

Will Diltiazem Lower Blood Pressure?

Yes, diltiazem effectively lowers blood pressure through its calcium channel blocking mechanism, which reduces peripheral vascular resistance and causes a modest fall in blood pressure. 1

Mechanism and Efficacy

Diltiazem inhibits calcium influx during membrane depolarization of vascular smooth muscle, producing relaxation of coronary vascular smooth muscle and dilation of both large and small coronary arteries. 1 This results in dose-dependent decreases in systemic blood pressure and peripheral resistance. 1

Dose-Response Relationship

The antihypertensive effect of diltiazem is clearly dose-dependent, with optimal blood pressure reduction typically requiring 240-540 mg/day. 2

• Doses of 240-480 mg/day once daily significantly lower both systolic and diastolic blood pressure in a dose-related fashion 3
• The 90-120 mg/day range represents a "no-effect dose" for hypertension 2
• Diltiazem is commonly underdosed in clinical practice, with 70% of prescriptions being for 180-240 mg doses, which are suboptimal for hypertension treatment 2
• Dose escalations from 180 mg to 360 mg to 540 mg daily result in incremental blood pressure reductions and increased responder rates 3

Clinical Evidence

Multiple randomized controlled trials demonstrate diltiazem's antihypertensive efficacy:

• In a dose-ranging trial of 275 patients, once-daily diltiazem (240-480 mg) significantly lowered trough systolic and diastolic blood pressure, with ambulatory monitoring confirming consistent decreases throughout the 24-hour dosing interval 3
• A study of 350 patients aged 55 or older showed mean supine diastolic blood pressure reduction of 8.65 mm Hg with diltiazem XR versus 2.75 mm Hg with placebo (P < 0.0001) 4
• Blood pressure control (diastolic BP ≤90 mm Hg or reduction ≥10 mm Hg) was achieved in 58% of patients receiving diltiazem versus 27% receiving placebo 4

Important Clinical Caveats

Diltiazem should NOT be used in patients with heart failure with reduced ejection fraction (HFrEF), as nondihydropyridine calcium channel blockers have myocardial depressant activity and clinical trials have demonstrated either no benefit or worse outcomes in these patients. 5

• The 2017 ACC/AHA hypertension guidelines explicitly state that nondihydropyridine CCBs (verapamil, diltiazem) are not recommended in patients with hypertension and HFrEF 5
• Diltiazem should not be used in patients with left ventricular systolic dysfunction 5
• Caution is required when combining diltiazem with beta-blockers due to additive effects on cardiac conduction and increased risk of bradyarrhythmias 6

Role in Hypertension Management

In patients with coronary artery disease and hypertension, diltiazem can be substituted for beta-blockers if beta-blockers are contraindicated or produce intolerable side effects, but only if there is no left ventricular dysfunction. 6

• The American Heart Association recommends beta-blockers as first-choice agents for hypertension in CAD patients, with calcium channel blockers as alternatives 5, 6
• Diltiazem is particularly useful in patients with angina, as it alleviates ischemia through coronary vasodilation and reduction in myocardial oxygen demand 1

Safety Profile

Diltiazem is generally well tolerated with a favorable side-effect profile:

• Adverse events are typically mild with incidence similar to placebo 3
• The incidence of side effects with diltiazem is approximately half that of older agents like reserpine (12.3% versus 27.1%) 7
• Symptomatic hypotension may occasionally occur 1
• Diltiazem prolongs AV node refractory periods and may rarely result in abnormally slow heart rates or second- or third-degree AV block (0.48% incidence) 1