Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
CARDIZEM vs CALAN
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
Diltiazem inhibits calcium influx into cardiac and vascular smooth muscle cells during depolarization by binding to L-type calcium channels. This results in coronary vasodilation, decreased myocardial oxygen demand, and negative chronotropic and inotropic effects.
Verapamil inhibits calcium ion influx through voltage-gated L-type calcium channels in cardiac and vascular smooth muscle, leading to decreased myocardial contractility, slowed AV conduction, and vasodilation.
Angina pectoris (chronic stable, vasospastic),Atrial fibrillation or atrial flutter (rate control),Hypertension
Angina pectoris (chronic stable, vasospastic, unstable),Essential hypertension,Supraventricular tachyarrhythmias (e.g., atrial fibrillation, atrial flutter, PSVT)
Oral: 30-120 mg three to four times daily; extended-release: 120-360 mg once daily. IV: Initial 0.25 mg/kg (max 25 mg) bolus over 2 minutes, may repeat in 15 minutes (0.35 mg/kg); maintenance: 5-15 mg/hour continuous infusion.
Initial: 80-120 mg orally 3 times daily; maintenance: 240-480 mg/day in 3-4 divided doses. IV: 5-10 mg over 2 minutes, may repeat after 15-30 minutes.
Terminal elimination half-life is 3.0-4.5 hours in healthy adults; may be prolonged to 7-9 hours in elderly, hepatic impairment, or renal impairment; clinically relevant for dosing frequency.
Terminal elimination half-life is 3-7 hours for immediate-release; can be prolonged to 12-16 hours with sustained-release due to slow absorption; increased in hepatic impairment.
Hepatic via CYP3A4; undergoes extensive first-pass metabolism; metabolites: desacetyl diltiazem (active, 40-50% potency), N-demethylated, and deacetylated forms.
Extensively metabolized in the liver via CYP3A4, CYP1A2, and CYP2C8 isoenzymes; undergoes N-dealkylation and O-demethylation; first-pass metabolism results in low bioavailability (20-35%).
Primarily hepatic metabolism with extensive first-pass effect; approximately 2-4% excreted unchanged in urine; fecal excretion accounts for about 65% of dose as metabolites; renal excretion accounts for about 35% of dose as metabolites.
Approximately 70% renal (3-4% unchanged, remainder as metabolites) and 25% biliary/fecal.
77-87% bound to plasma proteins, primarily albumin.
Approximately 90% bound to plasma proteins, primarily albumin.
3-5 L/kg; large Vd indicates extensive tissue binding and distribution.
Vd 4-5 L/kg; indicates extensive tissue distribution beyond plasma volume.
Oral: 40-50% due to significant first-pass metabolism (range 30-60% across individuals); IV: 100%.
Oral bioavailability is 20-35% due to extensive first-pass hepatic metabolism; IV bioavailability is 100%.
No specific dose adjustment for renal impairment; use with caution in severe renal dysfunction (Cr Cl <30 m L/min) with close monitoring of heart rate and blood pressure.
Cr Cl <30 m L/min: reduce dose by 50% and monitor carefully.
Child-Pugh Class A: No adjustment. Class B: Reduce total daily dose by 25-50%. Class C: Avoid use; if necessary, consider further dose reduction with careful monitoring.
Child-Pugh A: 50% of normal dose; Child-Pugh B: 25% of normal dose; Child-Pugh C: contraindicated or use with extreme caution.
Oral: 1.5-2 mg/kg/day divided every 6-8 hours, maximum 3.5 mg/kg/day. Extended-release not recommended in children. IV: Use only with caution; dosing not well established; typical initial bolus 0.1-0.3 mg/kg over 2 minutes, maximum 10 mg; infusion 0.5-5 mcg/kg/min.
Oral: 4-8 mg/kg/day in 3 divided doses; IV: 0.1-0.3 mg/kg over 2 minutes, max 5 mg.
Start at lower end of dosing range: oral immediate-release 30 mg three times daily; extended-release 120 mg once daily. Increase slowly. IV: Lower initial bolus (0.15-0.2 mg/kg) and infusion rates (2-5 mg/hour). Monitor for hypotension and bradycardia.
Start at lowest dose (e.g., 40 mg 3 times daily) and titrate slowly; monitor for hypotension and bradycardia.
There is no FDA black box warning for CARDIZEM (diltiazem).
Contains verapamil hydrochloride. Risk of serious adverse effects including hypotension, bradycardia, AV block, and cardiac arrest. Must not be administered to patients with severe left ventricular dysfunction, cardiogenic shock, or sick sinus syndrome (unless paced).
Symptomatic hypotension,Bradycardia or heart block (especially in sick sinus syndrome or AV block without pacemaker),Worsening heart failure in patients with reduced ventricular function,Hepatic injury (rare but elevated liver enzymes reported),Concomitant use with beta-blockers may increase risk of bradycardia and heart failure,Digitalis toxicity risk increased when used with digoxin,May exacerbate myasthenia gravis,Acute generalized exanthematous pustulosis (AGEP) and other severe cutaneous reactions,Gradual withdrawal recommended for chronic therapy to avoid angina exacerbation,May lower blood pressure, use with caution in patients with hypotension,Use in renal impairment: monitor carefully
May cause hypotension, bradycardia, AV block, and exacerbation of heart failure. Avoid in patients with pre-existing conduction abnormalities. Use caution with beta-blockers, digoxin, and CYP3A4 inhibitors. Abrupt withdrawal may exacerbate angina. May increase lithium and carbamazepine levels.
Hypersensitivity to diltiazem or any component,Sick sinus syndrome (except with functioning ventricular pacemaker),Second- or third-degree AV block (except with functioning pacemaker),Severe hypotension (systolic < 90 mm Hg),Acute myocardial infarction with pulmonary congestion,Atrial fibrillation or flutter associated with accessory bypass tract (e.g., WPW syndrome; risk of ventricular tachycardia or fibrillation),Cardiogenic shock,Concurrent use with ivabradine,Lactation (due to potential adverse effects in infants)
Severe left ventricular dysfunction, cardiogenic shock, sick sinus syndrome (without pacemaker), second- or third-degree AV block (without pacemaker), atrial flutter/fibrillation with accessory bypass tract (e.g., WPW syndrome), concurrent use of IV beta-blockers.
Avoid grapefruit and grapefruit juice as they inhibit CYP3A4 and can increase diltiazem levels, leading to toxicity. High-fat meals may increase absorption of some extended-release formulations; take with consistent meals. Alcohol may increase the risk of hypotension and dizziness. Maintain adequate hydration and avoid excessive salt intake to control blood pressure.
Avoid grapefruit and grapefruit juice as they inhibit CYP3A4 metabolism, increasing verapamil levels and risk of toxicity. Limit alcohol intake as it may enhance hypotensive effects. High-fat meals may delay absorption but not extent; take consistently with regard to meals.
No adequate studies in pregnant women. In animal studies, diltiazem (Cardizem) has been shown to cause skeletal abnormalities and increased fetal mortality at doses 5-10 times the maximum recommended human dose. Based on animal data and human experience with calcium channel blockers, risk cannot be ruled out. Use only if potential benefit justifies risk to fetus. Category C.
First trimester: No increased risk of major malformations observed in human studies; animal studies show fetal toxicity at high doses. Second and third trimesters: May cause fetal bradycardia, hypotension, and impaired placental perfusion; avoid use for pregnancy-induced hypertension due to risk of fetal hypoxia.
Diltiazem is excreted in human milk. A study reported a milk-to-plasma (M/P) ratio of approximately 0.9. The estimated infant dose is 1-2% of maternal weight-adjusted dose. Caution is advised; consider waiting 3-4 hours after dose before breastfeeding to minimize exposure.
Verapamil (CALAN) is excreted into breast milk; M/P ratio approximately 0.6. The relative infant dose is low (estimated <5% of maternal weight-adjusted dose). No adverse effects reported in breastfed infants. Caution in preterm infants or those with renal impairment.
Increased plasma volume and altered protein binding in pregnancy may reduce diltiazem concentrations; consider dose titration based on clinical response. No specific dose adjustment established; monitor therapeutic effect.
Pregnancy may increase clearance of verapamil; monitoring of therapeutic effect advised. Dose may need adjustment based on clinical response. Avoid use in pregnancy-induced hypertension.
Cardizem (diltiazem) is a non-dihydropyridine calcium channel blocker used for hypertension, angina, and atrial fibrillation/atrial flutter. It is contraindicated with IV beta-blockers due to risk of bradycardia and heart block. In AF, use IV form for rate control but avoid in WPW due to risk of ventricular pre-excitation. Diltiazem is metabolized by CYP3A4; caution with strong inhibitors like clarithromycin or grapefruit juice. For hypertension, start at 30 mg TID or extended-release once daily. Monitor heart rate and PR interval; avoid in sick sinus syndrome or second/third-degree AV block without pacemaker.
Calan (verapamil) is a class IV antiarrhythmic and calcium channel blocker. Use caution in patients with hepatic impairment due to reduced clearance; dose adjustment may be needed. Avoid in patients with pre-existing bradycardia, second- or third-degree AV block, or sick sinus syndrome unless a pacemaker is present. May increase digoxin levels; monitor digoxin concentrations. Use with caution in patients with hypertrophic cardiomyopathy. For IV administration, have calcium gluconate available to reverse hypotension or bradycardia. Not recommended for use in acute myocardial infarction or cardiogenic shock.
Take this medication exactly as prescribed; do not crush or chew extended-release capsules.,Avoid grapefruit and grapefruit juice while taking this medication.,If you miss a dose, take it as soon as you remember unless it is almost time for your next dose; do not double the dose.,Do not stop taking this medication abruptly, as it may worsen your condition.,Common side effects include dizziness, headache, and swelling in the ankles/feet; contact your doctor if you experience slow heartbeat, shortness of breath, or fainting.,This medication may cause dizziness or lightheadedness; avoid driving or operating machinery until you know how it affects you.
Take exactly as prescribed; do not skip doses or stop abruptly without consulting your doctor.,Avoid grapefruit juice as it can increase verapamil levels and risk of side effects.,If you miss a dose, take it as soon as you remember unless it is almost time for the next dose; do not double the dose.,Avoid alcohol as it may worsen side effects like dizziness or low blood pressure.,Report symptoms of bradycardia (slow heart rate), palpitations, shortness of breath, or swelling of ankles/feet.,This medication may cause dizziness; avoid driving or operating machinery until you know how it affects you.,Do not consume grapefruit or its juice during treatment.,Keep a regular medication schedule and do not change brands without doctor approval.
No interactions on record
No interactions on record
Explore head-to-head clinical comparisons of other medications in the same therapeutic classes.
Common clinical questions about CARDIZEM vs CALAN, answered by our medical review team.
CARDIZEM is a Calcium Channel Blocker that works by Diltiazem inhibits calcium influx into cardiac and vascular smooth muscle cells during depolarization by binding to L-type calcium channels. This results in coronary vasodilation, decreased myocardial oxygen demand, and negative chronotropic and inotropic effects.. CALAN is a Calcium Channel Blocker that works by Verapamil inhibits calcium ion influx through voltage-gated L-type calcium channels in cardiac and vascular smooth muscle, leading to decreased myocardial contractility, slowed AV conduction, and vasodilation.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between CARDIZEM and CALAN depend on the specific clinical indication. These are both Calcium Channel Blocker agents and are not directly interchangeable by dose. A physician or clinical pharmacist should guide any therapeutic switching decisions.
The standard adult dose of CARDIZEM is: Oral: 30-120 mg three to four times daily; extended-release: 120-360 mg once daily. IV: Initial 0.25 mg/kg (max 25 mg) bolus over 2 minutes, may repeat in 15 minutes (0.35 mg/kg); maintenance: 5-15 mg/hour continuous infusion.. The standard adult dose of CALAN is: Initial: 80-120 mg orally 3 times daily; maintenance: 240-480 mg/day in 3-4 divided doses. IV: 5-10 mg over 2 minutes, may repeat after 15-30 minutes.. Dosing should always be individualized based on indication, renal and hepatic function, age, and other patient factors.
No direct drug-drug interaction has been formally documented between CARDIZEM and CALAN in current clinical databases. However, individual patient risk factors including other medications, organ function, and comorbidities should always be evaluated by a qualified healthcare provider.
The maternal-fetal safety profiles differ. CARDIZEM is classified as Category C. No adequate studies in pregnant women. In animal studies, diltiazem (Cardizem) has been shown to cause skeletal abnormalities and increased fetal mortality at doses 5-10 times the . CALAN is classified as Category C. First trimester: No increased risk of major malformations observed in human studies; animal studies show fetal toxicity at high doses. Second and third trimesters: May cause fetal . Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.