Overview
Diltiazem is a calcium channel blocker used to treat hypertension and angina. It works by relaxing blood vessels and reducing heart rate, which lowers blood pressure and decreases myocardial oxygen demand. The extended-release formulation allows for once-daily dosing.
Mechanism of Action
Diltiazem inhibits calcium ion influx during depolarization in cardiac and vascular smooth muscle, resulting in coronary and peripheral vasodilation, reduced heart rate, and decreased myocardial contractility.
Indications
- Treatment of hypertension
- Management of chronic stable angina
- Management of angina due to coronary artery spasm
Common Doses
- 120 mg
- 180 mg
- 240 mg
- 300 mg
- 360 mg
- 420 mg
- 480 mg
Dosage
Starting dose typically 180-240 mg once daily for hypertension, 120-180 mg once daily for angina. Titrate based on response, with usual range 240-360 mg daily and maximum up to 480 mg daily. Adjustments should be made over 7-14 days.
Contraindications
- Sick sinus syndrome without functioning ventricular pacemaker
- Second- or third-degree AV block without functioning ventricular pacemaker
- Hypotension (<90 mm Hg systolic)
- Hypersensitivity to diltiazem
- Acute myocardial infarction with pulmonary congestion on admission x-ray
Side Effects
- Headache (5.4%)
- Dizziness (3.0%)
- Bradycardia (3.3%)
- First-degree AV block (3.3%)
- Edema (2.6%)
- Asthenia (1.8%)
- Constipation
- Nausea
- Rash
- Elevated liver enzymes
Interactions
- Beta-blockers: additive effects on cardiac conduction and blood pressure
- Digitalis: increased digoxin levels possible
- Other antihypertensives: additive hypotensive effects
- CYP3A4 inhibitors/inducers may affect diltiazem metabolism
Counseling Points
- Take once daily, with or without food
- Do not crush or chew extended-release capsules
- Report symptoms of slow heart rate, dizziness, or swelling
- Avoid grapefruit juice which may increase drug levels
- Rise slowly from sitting/lying position to prevent dizziness