Sounds like 'dil-TYE-a-zem'

Key points about diltiazem

  • Diltiazem is used to treat high blood pressure, irregular heart beat and to prevent chest pain (angina).
  • Diltiazem is also called Cardizem CD.
  • Find out how to take it safely and possible side effects. 
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Diltiazem is used to treat high blood pressure (hypertension) and to prevent chest pain (angina). It may help to increase your ability to exercise and decrease how often you get chest pain. Diltiazem may also be used to control your heart rate if you have a fast or irregular heartbeat (such as atrial fibrillation). It works by relaxing blood vessels which helps to lower blood pressure. Diltiazem belongs to a group of medicines called calcium channel blockers. In New Zealand diltiazem is available in different strengths of capsules (120 mg, 180 mg, 240 mg and 360 mg).

May 2021: Notification that diltiazem tablets are no longer available in New Zealand.
As of May 2021, diltiazem tablets (30mg and 60mg) are no longer available in New Zealand. If you are taking diltiazem tablets, talk to your doctor about other treatment options. 

Note: Diltiazem capsules are still available. 

  • The dose of diltiazem will be different for different people. Your doctor will tell you which dose is right for you.
  • Diltiazem capsules are slow release and are usually taken once a day.
  • Always take your diltiazem exactly as your doctor has told you. The pharmacy label on your medicine will tell you how much diltiazem to take, how often to take it, and any special instructions.

  • Timing: Diltiazem capsules are usually taken once a day. Take your dose at about the same time each day. You can take diltiazem capsules with or without food.
  • Swallow the capsules whole with a glass of water. Do not open or chew them. The slow-release capsules have been designed to release the right dose of medicine slowly. If you open or chew them, they will not work properly. 
  • Limit drinking alcohol while you are taking diltiazem. Alcohol may increase your chance of side-effects, such as feeling dizzy or light-headed.
  • Missed dose: If you forget your dose, take it as soon as you remember. But, if it is nearly time for your next dose, just take the next dose at the right time. Do not take double the dose.
  • Do not stop taking diltiazem suddenly. Speak to your doctor or nurse before stopping.

  • Do you have problems with your kidneys, lungs or liver?
  • Do you have heart problems such as heart failure, a slow heart rate, low blood pressure or have you had a heart attack recently?
  • Do you have diabetes?
  • Are you pregnant, trying for a baby or breastfeeding?
  • Are you taking any other medicines? This includes any medicines you buy without a prescription, such as herbal and complementary medicines.

If so, it’s important that you tell your doctor or pharmacist before you start diltiazem. Sometimes a medicine isn’t suitable for a person with certain conditions, or it can only be used with extra care.

Like all medicines, diltiazem can cause side effects, although not everyone gets them. Often side effects improve as your body gets used to the new medicine.

Side effects What should I do?
  • Headache
  • This is quite common when you first start taking diltiazem and usually goes away with time
  • Tell your doctor if troublesome or if it does not go away after a few days
  • Dizziness
  • Feeling light-headed
  • Feeling faint when you stand up
  • This is common when you first start taking diltiazem and usually goes away with time
  • Be careful when getting up from either lying down or sitting to avoid falls
  • Avoid drinking alcohol
  • Changes in your heartbeat (either too slow, too fast or irregular)
  • Chest tightness
  • Wheezing or trouble breathing
  • Swelling of the ankles or feet
  • Tell your doctor immediately or ring HealthLine 0800 611 116
Did you know that you can report a side effect to a medicine to CARM (Centre for Adverse Reactions Monitoring)? Report a side effect to a product(external link)

Diltiazem may interact with a few medications and herbal supplements, so check with your doctor or pharmacist before starting diltiazem or before starting any new medicines, including those you may buy over the counter.

The following links have more information on diltiazem.

Medsafe Consumer Information Sheet:
Cardizem CD(external link)
Dilzem(external link)

New Zealand Formulary Patient Information: Diltiazem (external link)(te reo Māori)(external link)(external link)


  1. Diltiazem hydrochloride(external link) New Zealand Formulary
  2. Medical management of stable angina pectoris(external link) BPAC, 2011
  3. An update on managing patients with atrial fibrillation(external link) BPAC, 2017

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Credits: Sandra Ponen, Pharmacist, Healthify He Puna Waiora. Healthify is brought to you by Health Navigator Charitable Trust.

Reviewed by: Angela Lambie, Pharmacist, Auckland

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