Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
DILTZAC 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 is a calcium channel blocker that inhibits calcium ion influx across cardiac and vascular smooth muscle cells, resulting in dilation of coronary and systemic arteries and decreased myocardial contractility and conduction velocity.
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.
Hypertension,Chronic stable angina,Atrial fibrillation or flutter,Paroxysmal supraventricular tachycardia,Off-label: Prevention of migraine, Raynaud's phenomenon
Angina pectoris (chronic stable, vasospastic, unstable),Essential hypertension,Supraventricular tachyarrhythmias (e.g., atrial fibrillation, atrial flutter, PSVT)
Oral: 30-120 mg 3-4 times daily; maximum 480 mg/day. IV: 0.25 mg/kg over 2 min, then 0.35 mg/kg after 15 min if needed; continuous infusion 5-15 mg/hour.
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: 3.5-5.0 hours (healthy adults). Prolonged in elderly (6-8 hours) and in hepatic impairment (10-12 hours).
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
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%).
Renal: 60-70% as metabolites, 2-4% unchanged; Biliary/Fecal: 20-30% as metabolites.
Approximately 70% renal (3-4% unchanged, remainder as metabolites) and 25% biliary/fecal.
80-85% bound to plasma proteins (albumin and alpha-1-acid glycoprotein).
Approximately 90% bound to plasma proteins, primarily albumin.
5-6 L/kg (suggests extensive tissue distribution).
Vd 4-5 L/kg; indicates extensive tissue distribution beyond plasma volume.
Oral immediate-release: 40-60% (due to extensive first-pass hepatic metabolism). Extended-release: 30-40%. Intravenous: 100%.
Oral bioavailability is 20-35% due to extensive first-pass hepatic metabolism; IV bioavailability is 100%.
No adjustment required for GFR >30 m L/min. For GFR 10-30 m L/min, reduce dose by 25%. For GFR <10 m L/min, reduce dose by 50%.
Cr Cl <30 m L/min: reduce dose by 50% and monitor carefully.
Child-Pugh A: no adjustment. Child-Pugh B: reduce dose by 50%. Child-Pugh C: reduce dose by 75%.
Child-Pugh A: 50% of normal dose; Child-Pugh B: 25% of normal dose; Child-Pugh C: contraindicated or use with extreme caution.
Oral: 1-3 mg/kg/day divided 3-4 times; maximum 3 mg/kg/day. IV: 0.25 mg/kg over 2 min; may repeat 0.35 mg/kg after 15 min; infusion 5-15 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 lowest dose (30 mg 3-4 times daily) due to increased bioavailability and reduced clearance; titrate slowly. IV dose: 0.2 mg/kg over 2 min.
Start at lowest dose (e.g., 40 mg 3 times daily) and titrate slowly; monitor for hypotension and bradycardia.
None.
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).
May cause heart block, bradycardia, exacerbation of heart failure, hypotension, and hepatotoxicity. Monitor liver function, ECG, and blood pressure. Avoid abrupt discontinuation; taper gradually.
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.
Sick sinus syndrome (except with pacemaker), second- or third-degree AV block (except with pacemaker), hypotension (systolic <90 mm Hg), cardiogenic shock, acute myocardial infarction with pulmonary congestion, hypersensitivity to diltiazem, concomitant use of ivabradine, and concurrent use with strong CYP3A4 inhibitors when diltiazem is given intravenously.
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; they may increase diltiazem levels and risk of side effects. Alcohol may enhance blood pressure-lowering effects and cause dizziness. A high-fat meal may increase absorption, but this is not clinically significant.
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.
First trimester: No definitive evidence of teratogenicity in animal studies; human data limited. Second and third trimesters: Chronic use may cause fetal bradycardia, hypoxia, and growth restriction due to maternal hypotension and reduced placental perfusion.
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 breast milk with low levels. Milk-to-plasma ratio is approximately 0.28. Caution advised; monitor infant for bradycardia and hypotension.
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.
No standard dose adjustment required; however, increased plasma volume may reduce drug levels. Titrate to therapeutic effect with careful blood pressure monitoring.
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.
Diltzac is a calcium channel blocker (diltiazem) used for hypertension, angina, and atrial fibrillation. Avoid in patients with sick sinus syndrome (without pacemaker), second/third-degree AV block, or severe hypotension. Use with caution in hepatic impairment and renal failure. Monitor heart rate and ECG for bradycardia. Adjust dose with CYP3A4 inhibitors (e.g., grapefruit) or inducers. Advise gradual withdrawal to avoid rebound hypertension.
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 exactly as prescribed; do not stop abruptly or change dose without consulting your doctor.,Avoid grapefruit and grapefruit juice while taking Diltzac.,Do not drive or operate heavy machinery if you experience dizziness or lightheadedness.,Monitor for signs of heart failure (swelling of ankles, feet, or sudden weight gain) and report immediately.,Your doctor may need to do regular blood tests to check liver function and monitor your heart rate and blood pressure.
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 DILTZAC vs CALAN, answered by our medical review team.
DILTZAC is a Calcium Channel Blocker that works by Diltiazem is a calcium channel blocker that inhibits calcium ion influx across cardiac and vascular smooth muscle cells, resulting in dilation of coronary and systemic arteries and decreased myocardial contractility and conduction velocity.. 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 DILTZAC 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 DILTZAC is: Oral: 30-120 mg 3-4 times daily; maximum 480 mg/day. IV: 0.25 mg/kg over 2 min, then 0.35 mg/kg after 15 min if needed; continuous infusion 5-15 mg/hour.. 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 DILTZAC 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. DILTZAC is classified as Category C. First trimester: No definitive evidence of teratogenicity in animal studies; human data limited. Second and third trimesters: Chronic use may cause fetal bradycardia, hypoxia, and . 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.