Diltiazem hydrochloride is a benzothiazepine-class calcium channel blocker indicated for the management of hypertension, chronic stable angina, and atrial arrhythmias. It functions by inhibiting the influx of calcium ions during cardiac and vascular smooth muscle depolarization, resulting in coronary and peripheral vasodilation with reduced myocardial oxygen demand. This profile provides a comprehensive, evidence-based overview for healthcare professionals, detailing its pharmacological profile, clinical applications, and essential safety considerations to support informed therapeutic decisions.

Features

• Active Ingredient: Diltiazem hydrochloride
• Available Formulations: Immediate-release tablets, extended-release capsules and tablets, intravenous solution
• Therapeutic Class: Calcium channel blocker (nondihydropyridine subclass)
• Mechanism of Action: Inhibits calcium ion influx across cardiac and smooth muscle cell membranes
• Bioavailability: Approximately 40% (subject to first-pass metabolism)
• Protein Binding: 70–80%
• Half-life: 3–4.5 hours (immediate-release); extended-release formulations provide 24-hour coverage
• Metabolism: Hepatic via CYP3A4; active metabolite: desacetyldiltiazem
• Excretion: Primarily renal (35%) and fecal (65%)

Benefits

• Effectively lowers blood pressure through reduced peripheral vascular resistance
• Decreases angina frequency by improving coronary blood flow and reducing myocardial oxygen consumption
• Provides rate control in atrial fibrillation and flutter through AV node conduction slowing
• May offer renal protective effects in hypertensive patients with proteinuria
• Lower incidence of peripheral edema compared to dihydropyridine calcium channel blockers
• Demonstrated efficacy in silent myocardial ischemia reduction

Common use

Diltiazem is primarily prescribed for the management of essential hypertension, either as monotherapy or in combination with other antihypertensive agents. It is equally effective in treating chronic stable angina pectoris by reducing coronary vasospasm and decreasing cardiac workload. The medication is also indicated for controlling ventricular rate in patients with atrial fibrillation or atrial flutter, particularly when beta-blockers are contraindicated or poorly tolerated. Off-label uses include Raynaud’s phenomenon, esophageal spasm, and migraine prophylaxis in selected cases.

Dosage and direction

Hypertension: Extended-release formulations typically start at 180–240 mg once daily, titrated to a maximum of 540 mg daily based on response. Angina: Immediate-release tablets: 30 mg four times daily, increasing to 120–180 mg daily in divided doses; extended-release: 120–180 mg once daily, maximum 480 mg daily. Atrial arrhythmias: Oral: 120–360 mg daily in divided doses; IV: 0.25 mg/kg over 2 minutes, followed by 0.35 mg/kg if needed, then infusion of 5–15 mg/hour. Administration with food minimizes gastrointestinal upset. Tablets should be swallowed whole; extended-release capsules may be opened and sprinkled on applesauce if swallowing difficulty exists.

Precautions

Monitor blood pressure and heart rate regularly, especially during initiation and titration. Use cautiously in patients with hepatic impairment (reduce dosage) or renal dysfunction (monitor parameters). May prolong PR interval; monitor ECG in patients with conduction abnormalities. Abrupt withdrawal may cause rebound angina; taper gradually. Use with caution in heart failure patients with preserved ejection fraction. Geriatric patients may require lower doses due to decreased clearance. Dental professionals should be informed of diltiazem use due to potential gingival hyperplasia risk.

Contraindications

Patients with sick sinus syndrome or second- or third-degree AV block (except with functioning pacemaker), severe hypotension (systolic <90 mmHg), acute myocardial infarction with pulmonary congestion, hypersensitivity to diltiazem or components, and concurrent IV beta-blocker use. Significant hepatic impairment (Child-Pugh class B or C) contraindicates use. Pregnancy category C: use only if potential benefit justifies potential fetal risk.

Possible side effect

Common (>10%): Headache, dizziness, edema, flushing, bradycardia. Less common (1–10%): Nausea, constipation, rash, fatigue, AV conduction disorders. Rare (<1%): Hepatotoxicity, gingival hyperplasia, leukopenia, thrombocytopenia, Stevens-Johnson syndrome. Cardiovascular: Hypotension, heart failure exacerbation, syncope. Neurological: Asthenia, somnolence, insomnia. Most side effects are dose-dependent and often diminish with continued therapy.

Drug interaction

Strong CYP3A4 inhibitors (clarithromycin, ketoconazole, ritonavir) increase diltiazem levels significantly. Beta-blockers may potentiate bradycardia and AV block. Digoxin levels increase by 20–50%; monitor closely. Statins (simvastatin, lovastatin) exposure increases; limit simvastatin to 10 mg daily. Cyclosporine levels may increase requiring dosage adjustment. Anesthetics may potentiate cardiovascular effects. Rifampin decreases diltiazem efficacy. Carbamazepine, phenytoin, and theophylline levels may increase.

Missed dose

If a dose is missed, take it as soon as remembered unless it is nearly time for the next dose. Do not double the dose to make up for a missed one. For once-daily formulations, if missed for more than 12 hours, skip and resume regular schedule. For multiple daily dosing, if remembered within 4 hours of next dose, skip missed dose. Maintain consistent timing to ensure stable therapeutic levels.

Overdose

Manifests as severe bradycardia, hypotension, heart failure, AV block, and cardiac arrest. Treatment includes gastric lavage if recent ingestion, activated charcoal, and cardiovascular support. IV calcium gluconate (1–3 g) may reverse hypotension and bradycardia. Atropine, vasopressors, and cardiac pacing may be required. Hemodialysis is not effective due to high protein binding. Contact poison control center immediately for guidance.

Storage

Store at controlled room temperature (20–25°C/68–77°F) in original container. Protect from moisture and light. Keep tightly closed. Do not store in bathroom or near sink. Keep all medications away from children and pets. Do not freeze liquid formulations. Discard unused medication after expiration date. Do not flush medications; dispose through proper medication take-back programs.

Disclaimer

This information is for educational purposes and does not replace professional medical advice, diagnosis, or treatment. Always consult qualified healthcare providers regarding medical conditions or before starting any therapy. Dosage and indications may vary based on individual patient factors, regional guidelines, and updated clinical evidence. The prescriber retains ultimate responsibility for appropriate medication selection and monitoring.

Reviews

“Diltiazem remains a cornerstone in our cardiology practice for rate control in atrial fibrillation. Its favorable side effect profile compared to verapamil makes it particularly useful in older patients.” – Cardiologist, 15 years experience

“Excellent first-line option for hypertension with comorbid angina. The extended-release formulation provides consistent 24-hour coverage with improved patient adherence.” – Internal Medicine Specialist

“Effective for rate control but requires careful monitoring in patients with conduction abnormalities. The drug interaction profile demands particular attention in polypharmacy patients.” – Clinical Pharmacist

“Patients generally tolerate diltiazem well, though peripheral edema can be a limiting factor. We often combine with low-dose ACE inhibitors to mitigate this effect.” – Nurse Practitioner, Cardiology