[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Pharmacology](https://durgical.com/en/pharmacology/) › [Calcium channel blockers](https://durgical.com/en/pharmacology/classes/calcium-channel-blockers/) › Diltiazem

[Pharmacology](https://durgical.com/en/pharmacology/) · [Calcium channel blockers](https://durgical.com/en/pharmacology/classes/calcium-channel-blockers/)

# Diltiazem

A calcium channel blocker that acts on both the heart and the arteries. Used for angina, high blood pressure and rate control in atrial fibrillation.

Updated 2026-11-01

- Class: [Calcium channel blockers](https://durgical.com/en/pharmacology/classes/calcium-channel-blockers/)
- Ion channel: L-type voltage-gated calcium channel (CaV1.2)
- ATC code: C08DB01

⇅**L-type voltage-gated calcium channel (CaV1.2)**Diltiazem

ⓘ The figure shows diltiazem bound to the rabbit skeletal-muscle L-type channel CaV1.1, which shares the binding site with the cardiac and vascular channel CaV1.2.

**Target in 3D:** L-type voltage-gated calcium channel (CaV1.2). PDB structure 6JPB (RCSB PDB, public domain). [View the structure at RCSB PDB](https://www.rcsb.org/structure/6JPB) · Drag to rotate · pinch to zoom

## Mechanism of action

Diltiazem, a benzothiazepine, blocks L-type calcium channels from inside the pore. In the sinus and AV nodes it slows the heart rate and AV conduction; in heart muscle it lowers contractility; in arterioles and coronary arteries it causes moderate vasodilation. The result is less oxygen demand, more coronary flow and slower ventricular rate in atrial fibrillation.

- Diltiazem blocks L-type calcium channels in the heart and arteries
- The sinus and AV nodes slow down
- Contractility falls and arterioles relax
- Less oxygen demand; slower ventricular rate

## Pharmacokinetics

**Absorption**
Well absorbed by mouth, with a large first-pass effect

**Metabolism**
Liver, by CYP3A4, which it also inhibits

**Half-life**
About 3 to 4.5 hours (immediate-release)

## Indications

- Angina, including vasospastic angina [Stable angina →](https://durgical.com/en/conditions/stable-angina/)
- High blood pressure (extended-release forms) [Arterial hypertension →](https://durgical.com/en/conditions/arterial-hypertension/)
- Temporary rate control in atrial fibrillation or flutter, and conversion of PSVT (intravenous) [Atrial fibrillation →](https://durgical.com/en/conditions/atrial-fibrillation/)

## Adverse effects

### Common

- Oedema
- Headache
- Dizziness
- Bradycardia and first-degree AV block
- Constipation, milder than with verapamil

### Serious (rare, important)

- High-grade AV block or severe bradycardia
- Worse heart failure in reduced ejection fraction
- Hypotension
- Liver injury (rare)

## Contraindications

- Sick sinus syndrome or second- or third-degree AV block without a functioning pacemaker
- Hypotension
- Acute myocardial infarction with pulmonary congestion
- IV form: atrial fibrillation or flutter with an accessory pathway (WPW), ventricular tachycardia, or IV beta blockers given close by

## Key interactions

**Beta blockers**
Added bradycardia, AV block and heart failure

**Simvastatin, lovastatin and other CYP3A4 substrates**
Diltiazem inhibits CYP3A4 and raises their levels (myopathy with statins)

**Rifampicin and other CYP3A4 inducers**
Diltiazem levels fall sharply

**Digoxin**
Added slowing of AV conduction

## What is monitored

- Heart rate and blood pressure
- ECG (PR interval) and continuous ECG with the IV form
- Signs of heart failure
- Liver tests if symptoms appear

## Administration and safety

- Oral forms: immediate- and extended-release are different products; extended-release forms are not crushed or chewed
- IV form: given with continuous ECG and blood pressure monitoring and resuscitation equipment at hand
- Some IV preparations need refrigeration: storage is checked on the label

## Nursing care

- Check apical pulse and blood pressure before giving it; hold and report bradycardia or hypotension
- During IV use, watch the ECG for AV block and the blood pressure closely
- Ask about breathlessness, oedema and weight gain
- Review other medicines for CYP3A4 interactions (statins, some antifungals and antibiotics)

## Pregnancy and breastfeeding

Animal studies showed harm and human data are limited; it is used in pregnancy only when the benefit justifies the risk.

## Memory aid

DILTiazem sits in the middle: it TILTs toward the heart less than verapamil and more than amlodipine.

## Test yourself

Think of the answer, then tap the question to see it.

## Why is IV diltiazem avoided in atrial fibrillation with WPW?

Blocking the AV node can push conduction down the accessory pathway, causing a very fast ventricular rate or ventricular fibrillation.

## Which enzyme does diltiazem inhibit, and which drug interaction follows?

CYP3A4: it raises levels of simvastatin and lovastatin, increasing the risk of myopathy.

## Diltiazem is in which chemical group of calcium channel blockers?

Benzothiazepines; it is a non-dihydropyridine that acts on both the heart and the vessels.

[Add to my cards (3)](https://durgical.app/estudiar/?add=/en/pharmacology/diltiazem/)

## Related drugs

- [Verapamil](https://durgical.com/en/pharmacology/verapamil/)
- [Amlodipine](https://durgical.com/en/pharmacology/amlodipine/)
- [Digoxin](https://durgical.com/en/pharmacology/digoxin/)

## Related conditions

- [Stable angina](https://durgical.com/en/conditions/stable-angina/)
- [Arterial hypertension](https://durgical.com/en/conditions/arterial-hypertension/)
- [Atrial fibrillation](https://durgical.com/en/conditions/atrial-fibrillation/)

[← Back to the class: Calcium channel blockers](https://durgical.com/en/pharmacology/classes/calcium-channel-blockers/)

Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.

Sources: [DailyMed - DILTIAZEM HYDROCHLORIDE tablet, film coated](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=14869f9e-6a66-4f75-b0fc-4d808b1ee85e) (DailyMed (U.S. National Library of Medicine), 2026); [DailyMed - DILTIAZEM HYDROCHLORIDE IN SODIUM CHLORIDE- diltiazem hydrochloride injection, solution](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=8bae87a5-2137-467e-a1ad-79b2bc075e07) (DailyMed (U.S. National Library of Medicine), 2026); [ATCDDD - ATC/DDD Index](https://atcddd.fhi.no/atc_ddd_index/?code=C08DB01) (WHO Collaborating Centre for Drug Statistics Methodology, 2026).

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Representative model, for educational purposes only.

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