Drug reference

Diltiazem

Benzothiazepine calcium channel blocker (non-dihydropyridine) · Antihypertensive

Also known as Diltiazem hydrochloride, Cardizem, Tiazac, Dilacor XR, Angizem, Dilzem

START

Check HR, BP, ECG (PR interval), LFTs. Avoid in patients on beta-blockers (additive bradycardia/AV block).

TYPICAL MAX

480mg/day ER. Do not exceed in hepatic impairment. Monitor for edema (dose-limiting in some patients).

STOP IF

HR <50 bpm, new AV block, SBP <90 mmHg, acute HF, hepatotoxicity (jaundice, LFTs >3x ULN).

WATCH

CYP3A4 interactions (simvastatin dose should not exceed 10mg, atorvastatin max 20mg). Edema common—distinguish from HF. Grapefruit juice increases levels.

CDSCO approvedSchedule HJan AushadhiNPPA price-controlledATC C08DB01

Dose laddermg/d

Renal dose adjustmenteGFR mL/min/1.73m²

KDIGO 2024 + manufacturer label

Pharmacokineticsplasma · t hours

ONSET: 1h · Onset 1-2 hours
PEAK: 5h · Tmax ER 4-6 hours
t½: 7h · t½ ER 5-10 hours
DURATION: 1d · 24 hours (ER)

EXCRETION

Hepatic metabolism; 2-4% renal unchanged

route + CYP

INTERACTIONS

12 major

incl. contraindicated

PREGNANCY

Limited human data; crosses placenta. Animal studies show embryotoxicity at high doses. Use only if benefit outweighs risk—prefer methyldopa or labetalol in pregnancy.

FDA category + note

Top interactionssee all 12 →

BucindololContraindicatedTextbookG&G 14e · p617
CeliprololContraindicatedTextbookG&G 14e · p617
CilostazoleContraindicatedTextbookKDT 7e · p555
Esmolol HydrochlorideContraindicatedTextbookG&G 14e · p617

Available in India

137 branded formulations and 1 fixed-dose combination. Look up specific brands in the Drugs workspace.

Jan Aushadhi — generic available at GoI pharmacies

Mechanism

Inhibits L-type calcium channel influx in vascular smooth muscle and cardiac muscle, causing vasodilation (↓BP), negative chronotropy (↓HR), negative inotropy, and decreased AV nodal conduction

Indications

HypertensionChronic stable anginaVasospastic (Prinzmetal's) anginaAtrial fibrillation/flutter rate control (IV form)Paroxysmal supraventricular tachycardia (IV)

Dosing

Adult: Hypertension/angina (ER): 120-240mg daily initially, titrate every 7-14 days to max 480mg/day (ER) or 360mg/day (IR). Usual range 240-360mg/day ER. AF rate control (IV): 0.25mg/kg IV bolus over 2 min, then 5-15mg/h infusion.
Pediatric: Not established for oral use in children. IV: limited data for SVT.
Renal adjustment: No adjustment needed; minimally renally excreted.
Hepatic adjustment: Reduce dose by 50% in hepatic cirrhosis; monitor ECG and BP.
Geriatric: Start at 120mg daily; slower titration; increased risk of hypotension and bradycardia.
Max dose: 480mg/day (ER); 360mg/day (IR divided TID-QID)

Pharmacokinetics

Onset

Oral: antihypertensive effect within 1-2 hours; IV: immediate

Peak effect

IR: Tmax 2-3h; ER: Tmax 4-6h (capsule), 11-18h (tablet)

Duration

IR: 6-8 hours; ER: 24 hours

Half-life

IR: 3.0-4.5h; ER: 5-10h (prolonged by continued absorption)

Bioavailability

~40% (extensive first-pass metabolism); ER similar to IR

Protein binding

70-80%

Metabolism

Extensive hepatic via CYP3A4; desacetyldiltiazem (active metabolite, 25-50% potency)

Excretion

~2-4% unchanged in urine; remainder as metabolites (biliary/renal)

Contraindications

Severe bradycardia
Second or third-degree AV block without pacemaker
Sick sinus syndrome without pacemaker
Cardiogenic shock
Acute MI with pulmonary congestion
Concurrent IV beta-blocker

Side effects

Common

Peripheral edemaHeadacheDizzinessBradycardiaFlushingConstipationFatigue

Serious

Severe bradycardia / heart block
Heart failure decompensation
Hypotension (especially IV)
Hepatotoxicity (elevated LFTs, rare)

Pregnancy & lactation

Pregnancy

Limited human data; crosses placenta. Animal studies show embryotoxicity at high doses. Use only if benefit outweighs risk—prefer methyldopa or labetalol in pregnancy.

Lactation

Excreted in breast milk in small amounts (~1% of maternal dose); generally considered compatible with breastfeeding. Monitor infant for bradycardia.

Drug interactions

Bucindolol

Contraindicated

Textbook

Increased propensity for AV block, severe bradycardia, and decreased left ventricular function.

Avoid concurrent administration. The concurrent administration of diltiazem with a beta blocker is contraindicated.

Source: G&G 14e · p617

Celiprolol

Contraindicated

Textbook

Increased propensity for AV block, severe bradycardia, and decreased left ventricular function.

Avoid concurrent administration. The concurrent administration of diltiazem with a beta blocker is contraindicated.

Source: G&G 14e · p617

Cilostazole

Contraindicated

Textbook

Increased plasma levels and toxicity of cilostazole.

Should not be administered along with inhibitors of CYP3A4.

Source: KDT 7e · p555

Esmolol Hydrochloride

Contraindicated

Textbook

Increased propensity for AV block, severe bradycardia, and decreased left ventricular function.

Avoid concurrent administration. The concurrent administration of diltiazem with a beta blocker is contraindicated.

Source: G&G 14e · p617

Ranolazine

Contraindicated

Database

Moderate CYP3A4 inhibitors; increase ranolazine levels and QT prolongation risk; also additive AV nodal effects.

Contraindicated. Consider amlodipine or beta-blocker instead.

Source: Kimi deep-research + Cla

Acalabrutinib

Severe

Database

Drug interaction classified as: metabolism

Source: DDInter

Acebutolol

Severe

Database

Increased propensity for AV block, severe bradycardia, and decreased left ventricular function.

Avoid concurrent administration. The concurrent administration of diltiazem with a beta blocker is contraindicated.

Source: DDInter

Alfentanil

Severe

Database

Drug interaction classified as: metabolism

Source: DDInter

Atazanavir

Severe

Database

Drug interaction classified as: synergy, metabolism

Source: DDInter

Atenolol

Severe

Database

Increased propensity for AV block, severe bradycardia, and decreased left ventricular function.

Avoid concurrent administration. The concurrent administration of diltiazem with a beta blocker is contraindicated.

Source: DDInter

Avanafil

Severe

Database

Drug interaction classified as: metabolism

Source: DDInter

Avapritinib

Severe

Database

Drug interaction classified as: metabolism

Source: DDInter

Related guidelines

Beta-blockers in hypertension

MOHFW · Cardiology · 2024

Primary PCI for acute coronary syndrome

ESC · Cardiology · 2026

Hypertrophic cardiomyopathy

ESC · Cardiology · 2026

Preoperative cardiac evaluation for non-cardiac surgery

AHA · Cardiology · 2025

Hypertension in adults

MOHFW · Cardiology · 2021

Ask House about Diltiazem

Continue into a citation-backed clinical answer with the drug context already attached.

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Sources: KD Tripathi 7e, Goodman & Gilman 14e, Harrison 22e, Katzung·Verified: 2026-05-19 · House clinical team·Cockpit curated: 2026-05-19