DurgicalDurgical
EN
Open the app

Pharmacology · 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

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

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.

  1. Diltiazem blocks L-type calcium channels in the heart and arteries
  2. The sinus and AV nodes slow down
  3. Contractility falls and arterioles relax
  4. 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

Adverse effects

Common

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

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.

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)

← Back to the class: 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 (DailyMed (U.S. National Library of Medicine), 2026); DailyMed - DILTIAZEM HYDROCHLORIDE IN SODIUM CHLORIDE- diltiazem hydrochloride injection, solution (DailyMed (U.S. National Library of Medicine), 2026); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026).

Spotted a mistake?We are always improving for the community. Tell us what is wrong and our team will review it.Report a mistake

Representative model, for educational purposes only.