Cardizem (diltiazem hydrochloride) is a prescription calcium channel blocker medication indicated for the management of hypertension, chronic stable angina, and atrial arrhythmias. Developed with advanced pharmaceutical technology, it functions by inhibiting calcium ion influx during cardiac and vascular smooth muscle depolarization, resulting in reduced peripheral vascular resistance and decreased myocardial oxygen demand. This comprehensive guide provides healthcare professionals and informed patients with detailed, evidence-based information regarding its pharmacological profile, clinical applications, and safety considerations.

Features

• Active ingredient: Diltiazem hydrochloride
• Available formulations: Extended-release capsules, immediate-release tablets, injectable solution
• Standard strengths: 30 mg, 60 mg, 90 mg, 120 mg, 180 mg, 240 mg, 300 mg (varies by formulation)
• Mechanism: Benzothiazepine derivative calcium channel blocker
• Half-life: Approximately 3–4.5 hours (immediate-release); 5–8 hours (extended-release)
• Bioavailability: Approximately 40% (subject to first-pass metabolism)
• Protein binding: 70–80%
• Primary metabolites: Desacetyldiltiazem, N-monodesmethyldiltiazem
• Excretion: Primarily renal (35%) and fecal (65%)

Benefits

• Effectively lowers systolic and diastolic blood pressure through vasodilation
• Reduces frequency and severity of angina episodes by decreasing myocardial oxygen demand
• Controls ventricular rate in atrial fibrillation and atrial flutter
• Offers flexible dosing regimens with multiple formulations for individualized treatment
• Demonstrates a favorable side effect profile compared to other antihypertensive classes
• May be used as monotherapy or in combination with other cardiovascular agents

Common use

Cardizem is primarily prescribed for the management of essential hypertension, either as first-line therapy or as an adjunct to other antihypertensive agents. It is equally effective in treating chronic stable angina pectoris, particularly in patients who cannot tolerate beta-blockers or nitrates. In cardiology practice, it is frequently employed for rate control in patients with atrial fibrillation or atrial flutter, especially when there are contraindications to digitalis preparations. Off-label uses may include prevention of migraine headaches, treatment of esophageal spasm, and management of hypertrophic cardiomyopathy, though robust clinical evidence for these indications remains limited.

Dosage and direction

Dosage must be individualized based on therapeutic response and tolerance. For hypertension: Initial dose typically ranges from 180–240 mg once daily (extended-release), titrated upward at 2-week intervals to a maximum of 540 mg daily. For angina: Starting dose is 120–180 mg once daily, with maximum recommended dose of 480 mg daily. For atrial arrhythmias: Intravenous administration requires careful titration (0.25 mg/kg actual body weight over 2 minutes), followed by continuous infusion if necessary. Oral maintenance dosing follows at 60–120 mg three times daily (immediate-release) or equivalent extended-release formulation. Administration with food may minimize gastrointestinal upset. Tablets should be swallowed whole; do not crush or chew extended-release formulations.

Precautions

Regular monitoring of blood pressure, heart rate, and ECG is essential during therapy. Use with caution in patients with impaired hepatic function (dose reduction required) or moderate renal impairment. May prolong AV conduction time; exercise caution in patients with preexisting conduction abnormalities. Peripheral edema may occur, typically dose-dependent. Abrupt withdrawal may precipitate angina exacerbation; gradual dose reduction is recommended. Elderly patients may exhibit increased sensitivity and require lower initial doses. Patients should avoid grapefruit juice due to potential inhibition of CYP3A4 metabolism.

Contraindications

Absolute contraindications include sick sinus syndrome (except with functioning ventricular pacemaker), second- or third-degree AV block (without pacemaker), hypotension (systolic <90 mmHg), acute myocardial infarction with pulmonary congestion, hypersensitivity to diltiazem or any component, and concurrent intravenous beta-blocker administration. Relative contraindications include heart failure with reduced ejection fraction, severe bradycardia, and hepatic impairment (Child-Pugh class B or C).

Possible side effect

Most common adverse reactions (≥5%) include headache, dizziness, edema, asthenia, and first-degree AV block. Less frequent side effects (1–5%) comprise flushing, nausea, rash, and elevated liver enzymes. Serious but rare adverse events (<1%) include symptomatic bradycardia, heart block, heart failure exacerbation, and severe hypotension. Dermatological reactions ranging from erythema to Stevens-Johnson syndrome have been reported. Periodic liver function monitoring is advised due to rare cases of hepatic injury.

Drug interaction

Significant interactions occur with: Beta-blockers (additive bradycardia and AV conduction depression), digoxin (increased serum concentrations by 20–50%), cyclosporine (increased nephrotoxicity risk), statins metabolized by CYP3A4 (increased myopathy risk), and anesthetics (enhanced cardiovascular depression). Moderate interactions with: Carbamazepine, phenytoin, and rifampin (reduced diltiazem efficacy), amiodarone (additive bradycardia), and lithium (increased neurotoxicity potential). Always review full medication profile before initiation.

Missed dose

If a dose is missed, take it as soon as remembered unless it is nearly time for the next scheduled dose. Do not double the dose to make up for a missed administration. For once-daily formulations, if missed for more than 12 hours, skip the missed dose and resume regular schedule. Consistent timing maintains stable plasma concentrations; advise patients to establish routine administration practices.

Overdose

Manifestations include severe bradycardia, heart failure, hypotension, and conduction abnormalities. Management involves cardiovascular monitoring and supportive care. Administer IV calcium gluconate (1 g) for hypotension and bradycardia. Atropine (0.6–1 mg IV) may be effective for symptomatic bradycardia. Cardiac pacing may be necessary for refractory bradycardia. 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 and out of reach of children. Do not store in bathroom or near kitchen sink. Discard any medication beyond expiration date. Do not transfer capsules to other containers as desiccant properties may be compromised.

Disclaimer

This information is for educational purposes only and does not constitute medical advice. Always consult with a qualified healthcare provider before starting, changing, or stopping any medication. Individual response to therapy may vary. Full prescribing information should be reviewed before administration. Not all possible uses, interactions, or adverse effects are listed here.

Reviews

Clinical trials demonstrate 70–80% of hypertensive patients achieve blood pressure control with Cardizem monotherapy. Angina studies show 40–60% reduction in nitrate usage and exercise tolerance improvement. In atrial fibrillation, 85% of patients achieve adequate rate control within 2–4 hours of intravenous administration. Long-term studies indicate maintained efficacy over 12–24 months with stable dosing. Patient satisfaction surveys report preference for once-daily formulations due to convenience and reduced side effect profile compared to immediate-release preparations.