Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
CARDIZEM CD 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 cell membranes, resulting in dilation of coronary arteries and peripheral arterioles, 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,Variant angina
Angina pectoris (chronic stable, vasospastic, unstable),Essential hypertension,Supraventricular tachyarrhythmias (e.g., atrial fibrillation, atrial flutter, PSVT)
Hypertension: 180-360 mg once daily orally. Angina: 120-360 mg once daily orally. Maximum dose: 480 mg/day.
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: 6-8 hours (single dose), prolonged to 10-15 hours with multiple dosing or in elderly/hepatic impairment. Clinical context: Therapeutic steady-state achieved in 2-4 days.
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; also undergoes deacetylation; substrate of P-glycoprotein.
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: ~2-4% (unchanged), Hepatic metabolism to multiple metabolites; ~65% renal (metabolites), ~35% fecal/biliary. Total clearance: 5-7 m L/kg/min.
Approximately 70% renal (3-4% unchanged, remainder as metabolites) and 25% biliary/fecal.
70-80% bound primarily to albumin (70%), also alpha-1 acid glycoprotein (10%). Binding saturable at high concentrations.
Approximately 90% bound to plasma proteins, primarily albumin.
Approximately 5.3 L/kg. Meaning: Extensive tissue distribution (3-5 L/kg); reflects high lipophilicity and wide distribution beyond plasma.
Vd 4-5 L/kg; indicates extensive tissue distribution beyond plasma volume.
Extended-release (Cardizem CD): ~40% (range 35-45%) due to extensive first-pass metabolism. Immediate-release: ~40-50%. IV: 100%.
Oral bioavailability is 20-35% due to extensive first-pass hepatic metabolism; IV bioavailability is 100%.
No specific GFR-based adjustment required, but use caution in severe renal impairment (Cr Cl <30 m L/min).
Cr Cl <30 m L/min: reduce dose by 50% and monitor carefully.
Child-Pugh Class A: start with 120 mg once daily. Child-Pugh Class B: start with 120 mg once daily, titrate cautiously. Child-Pugh Class C: contraindicated.
Child-Pugh A: 50% of normal dose; Child-Pugh B: 25% of normal dose; Child-Pugh C: contraindicated or use with extreme caution.
Not approved for pediatric use; safety and efficacy not established.
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 (120 mg once daily) due to increased risk of hypotension and bradycardia; 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,Risk of heart failure exacerbation in patients with impaired ventricular function,May slow AV conduction, leading to bradycardia or AV block,Hepatic and renal impairment caution,May exacerbate symptoms in patients with hypertrophic cardiomyopathy
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 in presence of functioning ventricular pacemaker),Hypotension (systolic < 90 mm Hg),Acute myocardial infarction with pulmonary congestion,Known hypersensitivity to diltiazem
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.
Grapefruit juice may increase diltiazem serum concentrations; avoid concurrent ingestion. Alcohol may enhance hypotensive effects. No significant food restrictions otherwise.
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.
Diltiazem, the active ingredient in Cardizem CD, is classified as Pregnancy Category C. Animal studies have demonstrated embryotoxicity and teratogenicity (skeletal abnormalities) at doses 5-10 times the maximum recommended human dose. There are no adequate and well-controlled studies in pregnant women. In humans, exposure during the first trimester may be associated with a small increased risk of congenital anomalies, particularly cardiac defects, though data are limited. During the second and third trimesters, use may be associated with potential risks of fetal growth restriction and preterm labor due to maternal hypotension and decreased uteroplacental perfusion. The drug should only be used if the potential benefit justifies the potential risk to the fetus.
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 into human milk at low concentrations; the milk-to-plasma (M/P) ratio is approximately 0.8. Limited data suggest that the estimated infant daily dose is less than 1% of the maternal weight-adjusted dose. While adverse effects in breastfed infants have not been reported, caution is advised due to potential for cardiovascular effects. The manufacturer recommends discontinuing breastfeeding or the drug, considering the importance of the drug to the mother.
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.
Pregnancy-induced increases in plasma volume and hepatic metabolism may reduce diltiazem concentrations, potentially requiring dose adjustments. However, specific pharmacokinetic studies in pregnant women are lacking. Clinical monitoring of therapeutic effect (e.g., blood pressure control) should guide dosing; gradual titration is recommended, and doses may need to be increased based on response. Avoid abrupt discontinuation.
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.
Diltiazem (Cardizem CD) is a nondihydropyridine calcium channel blocker; use with caution in patients with systolic heart failure (HFr EF) due to negative inotropic effects. Avoid concurrent use with beta-blockers due to risk of bradycardia and heart block. May increase dugoxin levels; monitor digoxin levels. Contraindicated in sick sinus syndrome or second/third-degree AV block without pacemaker. Also inhibits CYP3A4; monitor for interactions with statins (e.g., simvastatin dose limit 10 mg).
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 capsule whole; do not crush or chew. May be taken without regard to meals.,Do not stop abruptly; gradual taper advised to avoid rebound hypertension or ischemia.,Report symptoms of bradycardia (dizziness, fainting) or heart failure (swelling, shortness of breath).,Avoid grapefruit juice as it may increase drug levels and risk of side effects.,Use sunscreen and protective clothing due to possible photosensitivity.
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 CD vs CALAN, answered by our medical review team.
CARDIZEM CD 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 cell membranes, resulting in dilation of coronary arteries and peripheral arterioles, 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 CARDIZEM CD 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 CD is: Hypertension: 180-360 mg once daily orally. Angina: 120-360 mg once daily orally. Maximum dose: 480 mg/day.. 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 CD 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 CD is classified as Category C. Diltiazem, the active ingredient in Cardizem CD, is classified as Pregnancy Category C. Animal studies have demonstrated embryotoxicity and teratogenicity (skeletal abnormalities) . 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.