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Diltiazem

Brand names: Cardizem, Cartia XT, Tiazac

Diltiazem is a calcium channel blocker that lowers blood pressure, eases angina, and slows a fast heart rate in atrial fibrillation.

Brand namesCardizem, Cartia XT, Tiazac
Type of medicineCalcium channel blocker
Prescription?Prescription
ImportantThis page is general information, not a prescription. Don't start, stop, or change a medicine without talking to your provider or pharmacist.

Overview

It relaxes blood vessels and slows the heart's electrical signals.

What it's used for

  • High blood pressure
  • Chest pain (angina)
  • Controlling heart rate in atrial fibrillation or flutter

How to take it

  • Swallow extended-release capsules whole.
  • Don't switch between brands or forms without asking; they release differently.

Your dose depends on your health and other medicines. Always follow your prescription label, and ask your pharmacist if anything is unclear.

Side effects

Common side effects

  • Swollen ankles
  • Headache
  • Dizziness
  • Slow heartbeat
  • Constipation
Call 911Fainting or a very slow heartbeat
Call your provider todayShortness of breath or fast weight gain
Call 911A blistering, peeling, or widespread red rash, especially with fever

Warnings

  • Not used in some types of heart failure or heart block.

Other medicines, foods, and alcohol

  • Beta blockers and digoxin can slow the heart too much.
  • It raises levels of some statins (simvastatin, lovastatin), apixaban, rivaroxaban, and many others.
  • Grapefruit juice may raise its level.

Tell your provider and pharmacist about every medicine, vitamin, and supplement you take.

Pregnancy and breastfeeding

Talk with your provider.

Missed doses, overdose, and storage

If you miss a dose

Take it as soon as you remember, unless it's almost time for your next dose. Then skip the missed dose. Don't take two doses at once.

If someone takes too much

Call Poison Control at 1-800-222-1222 or get help online at poison.org. Call 911 if the person collapses, has a seizure, has trouble breathing, or can't be woken.

Storing it

Store at room temperature, away from heat and moisture (not in the bathroom), and out of reach of children and pets.

Conditions it's used for

Sources

Last updated 2026-11-13.