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Overview: Diltiazem is commonly used to treat high blood pressure and chest pain. It is in a class of medicines known as non-dihydropyridine calcium channel blockers. Common side effects include headache, nausea, fluid retention, and dizziness. Serious side effects may include heart rate or rhythm changes, low blood pressure, and severe skin reactions.

Uses

What is diltiazem used for?

Diltiazem is commonly used for the following conditions.

Diltiazem may also be used for other conditions as determined by your healthcare provider.

How does diltiazem work (mechanism of action)?

Diltiazem works by acting on the heart muscles and blood vessels to lower blood pressure and also to slow down heart rate. 

How is diltiazem supplied (dosage forms)?

Brands and other names

  • Cardizem
  • Cardizem CD
  • Cardizem LA
  • Cartia XT
  • Dilacor XR
  • Matzim LA
  • Taztia XT
  • Tiadylt ER
  • Tiazac

Dosage forms and strengths

  • 60 mg, 90 mg, 120 mg, 180 mg, 240 mg, 300 mg, 360 mg, 420 mg extended-release oral capsules
  • 120 mg, 180 mg, 240 mg, 300 mg, 360 mg, 420 mg extended-release oral tablets
  • 30 mg, 60 mg, 90 mg, 120 mg oral tablets

How should I store diltiazem?

Diltiazem should be stored at room temperature, between 68 F to 77 F (20 C to 25 C). It can be exposed to temperatures between 59 F to 86 F (15 C to 30 C), for shorter periods of time, such as when transporting it. Store in a cool, dry place and protect from light.   

Side Effects

What are the most common side effects of diltiazem?

The most common side effects of diltiazem are listed below. Tell your healthcare provider if you have any of these side effects that bother you.

  • Headache
  • Nausea
  • Fluid retention
  • Dizziness
  • Rash
  • Upset stomach
  • Heart rhythm changes (see below)
  • Heart rate changes (see below)
  • Feeling unusually weak or tired
  • Cough
  • Pain 

There may be other side effects of diltiazem that are not listed here. Contact your healthcare provider if you think you are having a side effect of a medicine. In the U.S., you can report side effects to the FDA at www.fda.gov/medwatch or by calling 800-FDA-1088. In Canada, you can report side effects to Health Canada at www.health.gc.ca/medeffect or by calling 866-234-2345.

What are the serious side effects of diltiazem?

While less common, the most serious side effects of diltiazem are described below, along with what to do if they happen.

Heart Rhythm Changes. Diltiazem may cause heart rhythm problems that can lead to an irregular heartbeat and fainting. In rare cases, this may cause the heart to suddenly stop beating (cardiac arrest). Some people have a higher risk of this, including people who already have heart disease or who take other medicines that affect the heart. Tell your healthcare provider right away if you have any of the following symptoms.

  • Chest pain
  • Shortness of breath
  • Feeling dizzy, lightheaded, or fainting
  • Feeling weak or easily tired.
  • Confusion
  • Changes in your heart rate or rhythm, such as fast, slow, pounding or skipping heartbeat

Heart Rate Changes. Diltiazem can make your heart beat slower than normal (bradycardia). Call your healthcare provider right away if you have any of the following symptoms of bradycardia. 

  • Feeling lightheaded, dizziness, or fainting
  • Confusion
  • Feeling weak or easily tired 
  • Slow heartbeat or feeling of skipped heartbeats 
  • Chest pain
  • Shortness of breath

Low Blood Pressure (Hypotension). Diltiazem may cause low blood pressure. If you feel faint or dizzy, lie down. Tell your healthcare provider right away if you have any of the following symptoms of low blood pressure. 

  • Dizziness, feeling lightheaded, or fainting
  • Confusion
  • Feeling weak or tired 

Heart Failure. Diltiazem may increase your risk of heart failure. Tell your healthcare provider right away if you have any of the following symptoms of heart failure.

  • Shortness of breath or trouble breathing, especially while lying down
  • Swelling in your feet, ankles, or legs
  • Unusually fast weight gain
  • Unusual tiredness

Liver Damage. Liver damage, also called hepatotoxicity, can happen when taking diltiazem. Call your healthcare provider right away if you have any of the following symptoms of liver damage.

  • Nausea or vomiting
  • Stomach or belly pain
  • Fever
  • Weakness or unusual tiredness
  • Itching
  • Loss of appetite
  • Light-colored poop
  • Dark-colored urine (pee)
  • Your skin or the whites of your eyes turning yellowish in color (also called jaundice)

Severe Skin Reactions. Diltiazem can cause severe skin reactions, called Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN), that can lead to death if not treated. If you develop a rash, stop diltiazem and call your healthcare provider right away. Get emergency help right away if you have any of the following symptoms of SJS or TEN. 

  • Painful red or purple skin that looks burned and peels off
  • Flat red rash or blisters on your skin, mouth, nose, and genitals 
  • Red, painful, watery eyes 

Severe Allergic Reactions. Diltiazem can cause allergic reactions, which can be serious. Stop taking diltiazem and get help right away if you have any of the following symptoms of a serious allergic reaction.

  • Breathing problems or wheezing
  • Racing heart
  • Fever or general ill feeling
  • Swollen lymph nodes
  • Swelling of the face, lips, mouth, tongue, or throat
  • Trouble swallowing or throat tightness
  • Itching, skin rash, or pale red bumps on the skin called hives
  • Nausea or vomiting
  • Dizziness, feeling lightheaded, or fainting
  • Stomach cramps
  • Joint pain

Warnings & Precautions

Who should not use diltiazem?

Allergies to Ingredients. People who are allergic to any of the following should not take diltiazem.

  • Cardizem
  • Cardizem CD
  • Cardizem LA
  • Cartia XT
  • Matzim LA
  • Taztia XT
  • Tiadylt ER
  • Tiazac
  • Diltiazem
  • Any of the ingredients in the specific product dispensed

Your pharmacist can tell you all of the ingredients in the specific diltiazem products they stock.

Sick Sinus Syndrome. People with sick sinus syndrome, which is a heart rhythm problem, should not take diltiazem unless they have a working pacemaker. 

Heart Block. Diltiazem should not be taken if the electrical signals in your heart move too slow (heart block).

Low Blood Pressure. People who have low blood pressure, which is called hypotension, should not take diltiazem. 

What should I know about diltiazem before using it?

Do not take diltiazem unless it has been prescribed to you by a healthcare provider. Take it as prescribed.

Do not share diltiazem with other people, even if they have the same condition as you. It may harm them.

Keep diltiazem out of the reach of children.

If you are taking diltiazem extended-release tablets or capsules, swallow them whole. Do not chew, cut, or crush them.

Some diltiazem extended-release capsules can be opened and sprinkled onto a spoonful of applesauce. Ask your healthcare provider if you can do this with the product you take. 

Diltiazem immediate-release tablets can be crushed or chewed. If the diltiazem immediate-release tablets you take are scored (have a break line in the tablet), they may be split. Ask your pharmacist or other healthcare provider if you are unsure how to take your medicine.

Diltiazem can make your skin more sensitive to light from the sun, sunlamps, and tanning beds. This is called photosensitivity. Exposure to this light can cause severe sunburns, blisters, and swelling. If you need to be in sunlight, wear sunscreen, a hat, and clothing that covers your skin.

What should I tell my healthcare provider before using diltiazem?

Tell your healthcare provider about all of your health conditions and any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. This will help them determine if diltiazem is right for you.

In particular, make sure that you discuss any of the following.

Current and Past Health Conditions. Tell your healthcare provider if you have any of the following.

  • Irregular heart rate or rhythm
  • Heart disease, including heart failure
  • History of a heart attack
  • Low blood pressure, also called hypotension
  • Liver problems
  • History of a severe skin reaction, such as Stevens-Johnson syndrome (SJS) or toxic epidermal necrolysis (TEN) 

Other Medicines and Supplements. Diltiazem may interact with other medicines and supplements. Before taking diltiazem, tell your healthcare provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. See the Interactions section below for more details.

Pregnancy. It is not known if or how diltiazem could affect pregnancy or harm an unborn baby. Tell your healthcare provider if you are or plan to become pregnant. Your healthcare provider will advise you if you should take diltiazem while you are pregnant or trying to get pregnant. 

Breastfeeding. Diltiazem passes into breast milk. Tell your healthcare provider if you are breastfeeding or plan to breastfeed. Your healthcare provider will advise you if you should take diltiazem while breastfeeding. 

Interactions

Does diltiazem interact with foods or drinks?

There are no known interactions between diltiazem and foods.

It is unknown if drinking alcohol will affect diltiazem. The risk of dizziness and low blood pressure may be increased if you drink alcohol while taking diltiazem. It is best to limit the amount of alcohol you drink.  

Does diltiazem interact with other medicines (drug interactions)?

Always tell your healthcare provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using.

In particular, make sure that you discuss if you are using any of the following before using diltiazem.

  • A benzodiazepine, such as clonazepam (Klonopin), diazepam (Valium and others), or lorazepam (Ativan and others), which is a medicine used for anxiety, muscle spasms, or seizures
  • A beta-blocker, such as metoprolol (Lopressor, Toprol XL, and others), atenolol (Tenormin), or propranolol (Inderal LA, Innopran XL), which is a medicine that may be used for certain heart conditions or to reduce blood pressure
  • Buspirone, which is a medicine used to treat anxiety
  • Carbamazepine (Carbatrol, Tegretol, and others), which is a medicine commonly used to treat seizures or nerve pain
  • Cimetidine (Tagamet HB), which is a medicine used for heartburn
  • Clonidine (Catapres-TTS and others), which is a medicine used for high blood pressure or attention deficit hyperactivity disorder (ADHD)
  • Cyclosporine (Gengraf, Neoral, Sandimmune, and others), which is a medicine that suppresses your immune system
  • Digoxin (Lanoxin), which is a medicine used to treat irregular heartbeat and some types of heart failure
  • Ivabradine, which is used to treat heart failure
  • Quinidine, which is used to treat an irregular heartbeat (arrhythmia)  
  • Rifampin, which is a medicine commonly used to treat an infection called tuberculosis
  • A statin, such as atorvastatin (Lipitor and others), lovastatin, or rosuvastatin (Crestor), which is a medicine to lower cholesterol

Some other medicines may alter the blood levels of diltiazem, and vice versa. Tell your healthcare provider about all medicines that you take or have recently taken. 

This may not be a complete list of medicines that can interact with diltiazem. Always check with your healthcare provider.

Does interact with other drugs you are taking?

Enter your medication into the WebMD interaction checker

Overdose/Missed Dose

What should I do if I accidentally use too much diltiazem?

If you or someone else has used too much diltiazem, get medical help right away, call 911, or contact a Poison Control center at 800-222-1222.

What should I do if I miss a dose of diltiazem?

If you miss a dose, take it as soon as you remember. If it is almost time for your next dose, skip the missed dose and only take the next dose. Do not take double or extra doses.