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Generic name: diltiazemdil-TYE-a-zem ]
Dosage form: extended-release capsules (120 mg; 180 mg; 240 mg; 300 mg; 360 mg; 420 mg)
Drug classes: Calcium channel blockers, Group IV antiarrhythmics

Medically reviewed by Philip Thornton, DipPharm. Last updated on Aug 22, 2023.

What is Tiazac?

Tiazac extended-release capsules are used in adults alone or in combination with other medicines to treat hypertension (high blood pressure) or symptoms of chronic stable angina. (chest pain). Lowering blood pressure may lower your risk of a stroke or heart attack.

Tiazac belongs to a class of medications called calcium-channel blockers. It works by relaxing the blood vessels so the heart does not have to pump as hard.

Tiazac also increases the supply of blood and oxygen to the heart.

Tiazac side effects

Get emergency medical help if you have signs of an allergic reaction to Tiazac (hives, difficult breathing, swelling in your face or throat) or a severe skin reaction (fever, sore throat, burning eyes, skin pain, red or purple skin rash with blistering and peeling).

Diltiazem may cause serious side effects. Call your doctor at once if you have:

Common Tiazac side effects may include:

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Before taking this medicine

You should not use Tiazac if you are allergic to diltiazem, or if you have:

You may not be able to use Tiazac if you have:

To make sure Tiazac is safe for you, tell your doctor if you have ever had:

It is not known whether diltiazem will harm an unborn baby. Tell your doctor if you are pregnant or plan to become pregnant.

Tell your doctor if you are breastfeeding.

How should I use Tiazac?

Take Tiazac extended-release capsules exactly as prescribed by your doctor. Follow all directions on your prescription label and read all medication guides or instruction sheets. Your doctor may occasionally change your dose. Use the medicine exactly as directed.

Your dose needs may change if you switch to a different brand, strength, or form of diltiazem.

Swallow Tiazac extended-release capsules whole. Do not crush or chew. The extended release capsules may also be administered by carefully opening the capsule and sprinkling the capsule contents on a spoonful of applesauce. The applesauce should be swallowed immediately without chewing and followed with a glass of cool water to ensure complete swallowing of the capsule contents. The applesauce should not be hot, and it should be soft enough to be swallowed without chewing. Any capsule contents/applesauce mixture should be used immediately and not stored for future use. Subdividing the contents of a Tiazac extended-release capsule is not recommended.

Your blood pressure and liver function will need to be checked often.

If you have high blood pressure, keep using this medicine even if you feel well. High blood pressure often has no symptoms.

Store at room temperature away from moisture, heat, and light.

What happens if I miss a dose?

Take Tiazac as soon as you can, but skip the missed dose if it is almost time for your next dose. Do not take two doses at one time.

What happens if I overdose?

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

Overdose symptoms may include low blood pressure, slow heart rate, severe dizziness, or fainting.

What should I avoid while using Tiazac?

Avoid taking an herbal supplement containing St. John's wort.

Avoid getting up too fast from a sitting or lying position, or you may feel dizzy. Avoid driving or hazardous activity until you know how this medicine will affect you. Your reactions could be impaired.


You should not use Tiazac if you have very low blood pressure, a serious heart condition such as "sick sinus syndrome" or "AV block" (unless you have a pacemaker), or if you have recently had a heart attack and you have a build-up of fluid in your lungs.

Before taking Tiazac extended-release capsules, tell your doctor if you have kidney disease, liver disease, or congestive heart failure.

Tiazac may impair your thinking or reactions. Be careful if you drive or do anything that requires you to be alert. Do not stop taking this medication without first talking to your doctazor. If you stop taking Tiazac suddenly, your condition may become worse.

Tiazac may be only part of a complete program of treatment that also includes diet, exercise, and other medications. Follow your diet, medication, and exercise routines very closely.

If you are being treated for high blood pressure, keep using this medicine even if you feel well. High blood pressure often has no symptoms. You may need to use blood pressure medicine for the rest of your life. However, if you have symptoms of low blood pressure (dizziness, fainting, weakness, or blurred vision), call your doctor and stop taking Tiazac.

What other drugs will affect Tiazac?

Sometimes it is not safe to use certain medicines at the same time. Some drugs can affect your blood levels of other drugs you use, which may increase side effects or make the medicines less effective.

Many drugs can interact with diltiazem. This includes prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible interactions are listed here. Tell your doctor about all other medicines you use.


Active ingredient: diltiazem hydrochloride
Inactive ingredients: black iron oxide, D& C Red No. 28, ethyl acrylate and methyl methacrylate copolymer dispersion, FD& C Blue No. 1, FD& C Green No. 3, FD& C Red No. 40, gelatin, hypromellose, magnesium stearate, microcrystalline cellulose, polysorbate, povidone, simethicone, sucrose stearate, talc, and titanium dioxide.


Manufactured by: Bausch Health Companies Inc., Steinbach, MB R5G 1Z7, Canada.
Distributed by: Bausch Health US, LLC, Bridgewater, NJ 08807, USA.

Further information

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use Tiazac only for the indication prescribed.

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.