Sounds like 'dil-TYE-a-zem'

Easy-to-read medicine information about diltiazem – what is it, how to take diltiazem safely and possible side effects.

Type of medicine Also called
  • Antihypertensive (to lower blood pressure)
  • Can also be used to prevent chest pain (angina)
  • Belongs to a group of medicines called calcium channel blockers
  • Apo-Diltiazem®
  • Cardizem CD®
  • Dilzem®

What is diltiazem?

  • 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 may get angina attacks.
  • 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 blocking calcium channels in the body, and in that way relaxes blood vessels and lowers blood pressure.
  • It belongs to a group of medicines called calcium channel blockers.
  • Diltiazem is available as immediate release tablets or modified release capsules.


  • The dose of diltiazem will be different for different people.
  • Diltiazem is available in 2 forms - as immediate release tablets or modified release capsules. Check with your pharmacist which version you are taking.
  • 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.
  • Each time you collect a new supply of diltiazem, check to make sure you have been given the same type of tablets or capsules as before.

How to take diltiazem

  • If you are prescribed the immediate release tablets, take these as you have been prescribed (usually 3 or 4 times a day). Take your doses at the same times each day.
  • If you are prescribed the modified release capsules, take these once a day. Swallow the modified release capsules whole, with a glass of water. Do not crush or chew them.
  • You can take diltiazem with or without food.
  • Limit or avoid drinking alcohol while you are taking diltiazem. Alcohol may increase your chance of side-effects, such as feeling dizzy or light-headed.
  • If you forget your dose, take it as soon as you remember that day. 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.

Possible side effects

Like all medicines, diltiazem can cause unwanted side effects, although not everyone gets them. Often unwanted 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 heart beat (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


  • Check with a pharmacist before taking over the counter medicines such as:
    • Cold or flu tablets containing phenylephrine (e.g. Sudafed PE), or diphenhydramine (e.g. Benadryl Original)
    • Anti-inflammatories such as diclofenac (e.g. Voltaren Rapid), ibuprofen (e.g. Nurofen), mefenamic acid (e.g. Ponstan), naproxen (e.g. Naprogesic)
  • 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.

Learn more

The following links provide further information on diltiazem.

Medsafe Consumer Information Sheet:
Cardizem CD

New Zealand Formulary Patient Information: Diltiazem

Credits: Sandra Ponen, Pharmacist, NZ. Reviewed By: Dr J Bycroft, GP