Diltiazem
Non-Dihydropyridine Calcium Channel Blocker
Generic Name
Diltiazem
Drug Class
Calcium channel blocker (non-dihydropyridine)
Indications
- Hypertension
- Chronic stable angina
- Variant (Prinzmetal) angina
- Supraventricular tachyarrhythmias (e.g., atrial fibrillation, atrial flutter)
Dosage
- Hypertension / Angina (oral): 120–240 mg/day in divided doses or as extended-release once daily; max 360 mg/day
- Arrhythmias (IV): 0.25 mg/kg IV bolus over 2 minutes; may repeat 0.35 mg/kg after 15 minutes if needed
- Maintenance IV infusion: 5–15 mg/hour
- Children: Specialist use only; dose individualized
Note: Dose adjustment required in hepatic or renal impairment.
Route of Administration
Oral (tablet, capsule), Intravenous
Mechanism of Action
Diltiazem inhibits calcium influx into myocardial and vascular smooth muscle cells. It reduces heart rate, slows atrioventricular nodal conduction, decreases myocardial contractility, and causes coronary and peripheral vasodilation.
Common Adverse Effects
- Bradycardia
- Peripheral edema
- Headache
- Dizziness
- Constipation
Serious Adverse Effects
- Severe hypotension
- Heart block or sinus arrest
- Heart failure exacerbation
- Hepatic dysfunction (rare)
Contraindications
- Sick sinus syndrome (without pacemaker)
- Second- or third-degree AV block
- Severe hypotension
- Acute heart failure with reduced ejection fraction
- Hypersensitivity to diltiazem
Precautions
- Monitor heart rate and blood pressure regularly
- Use caution when combined with beta-blockers
- Adjust dose in hepatic or renal impairment
- Avoid abrupt discontinuation
Drug Interactions
- Beta-blockers – increased risk of bradycardia or heart block
- Digoxin – increases digoxin levels
- Statins (simvastatin) – increased risk of myopathy
- CYP3A4 inhibitors or inducers – altered diltiazem levels
Pregnancy & Lactation
Use only if benefit outweighs risk. Excreted in breast milk; monitor infant for bradycardia.
Patient Counseling
- Take medication at the same time each day
- Do not crush extended-release formulations
- Monitor pulse and blood pressure
- Report dizziness, swelling, or slow heartbeat