Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
DILACOR XR 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 ion influx across cardiac and vascular smooth muscle cells, resulting in dilation of coronary and systemic arteries, decreased myocardial contractility, and reduced sinoatrial and atrioventricular 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.
Angina pectoris due to coronary artery spasm (Prinzmetal's variant angina),Chronic stable angina,Essential hypertension
Angina pectoris (chronic stable, vasospastic, unstable),Essential hypertension,Supraventricular tachyarrhythmias (e.g., atrial fibrillation, atrial flutter, PSVT)
180 to 240 mg orally once daily, administered on an empty stomach; maximum dose 480 mg once daily.
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 half-life: 6-12 hours (prolonged in elderly, hepatic impairment, or with CYP3A4 inhibitors)
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.
Extensively metabolized in the liver via CYP3A4; undergoes deacetylation and N-demethylation.
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 (70% as metabolites, 3-4% as unchanged drug); biliary/fecal (25-30%)
Approximately 70% renal (3-4% unchanged, remainder as metabolites) and 25% biliary/fecal.
98-99% bound to serum albumin and alpha-1-acid glycoprotein
Approximately 90% bound to plasma proteins, primarily albumin.
1.1-1.8 L/kg (high Vd indicates extensive tissue binding)
Vd 4-5 L/kg; indicates extensive tissue distribution beyond plasma volume.
Oral: 40-50% (first-pass metabolism; food does not affect extent)
Oral bioavailability is 20-35% due to extensive first-pass hepatic metabolism; IV bioavailability is 100%.
GFR 30-60 m L/min: initiate at 120 mg once daily, titrate cautiously; GFR <30 m L/min: not recommended due to risk of accumulation.
Cr Cl <30 m L/min: reduce dose by 50% and monitor carefully.
Child-Pugh Class A: initiate at 120 mg once daily; Child-Pugh Class B or C: avoid use.
Child-Pugh A: 50% of normal dose; Child-Pugh B: 25% of normal dose; Child-Pugh C: contraindicated or use with extreme caution.
Safety and effectiveness in pediatric patients have not been established; no dosing recommendations.
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 low end of dosing range (120 mg once daily) due to increased systemic exposure and risk of hypotension; titrate slowly.
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 hypotension, bradycardia, and heart block; avoid in patients with sick sinus syndrome or second- or third-degree AV block without a pacemaker; caution in patients with congestive heart failure; may increase risk of digitalis toxicity; abrupt withdrawal may worsen angina.
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 in presence of functioning ventricular pacemaker), second- or third-degree AV block (except with pacemaker), hypotension (systolic < 90 mm Hg), acute myocardial infarction with pulmonary congestion, hypersensitivity to diltiazem, concurrent use of ivabradine.
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 plasma concentrations, leading to increased risk of adverse effects. Avoid high-fat meals as they may affect the absorption of the extended-release formulation.
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.
DILACOR XR (diltiazem) is a calcium channel blocker with limited human pregnancy data. In animal studies, at doses up to 5 times the maximum recommended human dose, no teratogenic effects were observed. However, embryofetal toxicity (increased fetal loss, growth retardation) occurred at maternally toxic doses. First trimester: No adequate human studies; risk cannot be excluded. Second and third trimesters: Use only if clearly needed; may cause maternal hypotension and reduced uteroplacental blood flow, potentially leading to fetal hypoxia and growth restriction. U. S. FDA Pregnancy 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 breast milk. The milk-to-plasma (M/P) ratio ranges from 0.7 to 0.9. Limited data suggest infant exposure is low (approximately 1% of maternal weight-adjusted dose). No adverse effects reported in breastfed infants. Caution advised; monitor infant for bradycardia, hypotension, and sedation. Alternative agents may be preferred.
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.
Plasma volume and renal clearance increase during pregnancy, potentially reducing diltiazem concentrations. However, specific pharmacokinetic studies are lacking. Clinical response and blood pressure should guide dosing. Start at the lowest effective dose and titrate based on maternal heart rate and blood pressure. Avoid sustained-release formulations if rapid titration needed; immediate-release may be used. Monitor for hypotension, which may worsen uteroplacental perfusion. No specific dose adjustment recommended in published guidelines; use caution and individualized dosing.
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.
DILACOR XR is a sustained-release formulation of diltiazem, a calcium channel blocker. Do not crush or chew the capsule; swallowing whole is essential for extended-release properties. Monitor heart rate and blood pressure regularly due to risk of bradycardia and hypotension. Use with caution in patients with reduced hepatic function as diltiazem undergoes extensive first-pass metabolism. Avoid concurrent use with strong CYP3A4 inhibitors (e.g., ketoconazole) as they can increase diltiazem levels. In patients with atrial fibrillation or flutter, it may be used for rate control but contraindicated in sick sinus syndrome or second/third-degree AV block without a 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.
Swallow DILACOR XR capsules whole; do not crush, chew, or break them.,Take this medication exactly as prescribed, usually once daily. Do not stop suddenly without consulting your doctor.,Avoid grapefruit and grapefruit juice as they can increase the effects and side effects of diltiazem.,Limit alcohol intake as it may increase the risk of dizziness or fainting.,Notify your doctor if you experience slow heartbeat, shortness of breath, swelling of ankles/feet, or severe dizziness.,Keep a record of your blood pressure and pulse at home and bring it to appointments.,Do not take other medications, including over-the-counter products or herbal supplements, without consulting your healthcare provider.
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 DILACOR XR vs CALAN, answered by our medical review team.
DILACOR XR is a Calcium Channel Blocker that works by Diltiazem inhibits calcium ion influx across cardiac and vascular smooth muscle cells, resulting in dilation of coronary and systemic arteries, decreased myocardial contractility, and reduced sinoatrial and atrioventricular 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 DILACOR XR 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 DILACOR XR is: 180 to 240 mg orally once daily, administered on an empty stomach; maximum dose 480 mg once daily.. 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 DILACOR XR 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. DILACOR XR is classified as Category C. DILACOR XR (diltiazem) is a calcium channel blocker with limited human pregnancy data. In animal studies, at doses up to 5 times the maximum recommended human dose, no teratogenic . 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.