Diltiazem extended-release oral capsule side effects: A detailed guide

This article describes possible side effects of diltiazem ER oral capsule. (ER means the drug is released slowly over time in your body.) You’ll also find information on cost savings and coupon options for diltiazem. You can explore this overview article to learn more about diltiazem ER oral capsule, including the drug’s uses, side effects, and more.

Diltiazem ER oral capsule is a generic version of the brand-name drugs Cardizem CD, Cartia XT, Tiazac, and Taztia XT. Several different versions of diltiazem oral capsule are available. If your capsules look different than usual, check with your pharmacist to ensure you’ve received the specific form of diltiazem that your doctor prescribed.

Diltiazem also comes in other oral forms, but these forms aren’t described in this article. To learn more about these forms, talk with your doctor.

More common side effects of diltiazem

Diltiazem extended-release (ER) oral capsule may cause mild or serious side effects. Below are some of the more common side effects of this medication.

Commonly reported side effects of diltiazem ER oral capsule include:

• headache
• dizziness
• swelling due to fluid buildup
• weakness
• slow heart rate*

* To learn more about this side effect, see the “Side effects of diltiazem in detail” section below.

Mild side effects of diltiazem

Diltiazem may cause certain mild side effects. Most often, mild side effects are temporary and can be easily managed. Tell your doctor or pharmacist if you have side effects that don’t go away or become bothersome.

Mild side effects of diltiazem extended-release (ER) oral capsule that occurred in studies include:

• headache
• dizziness
• swelling due to fluid buildup
• weakness
• tremor
• nervousness
• sleepiness
• constipation or diarrhea
• dry mouth
• unusual taste in the mouth
• upset stomach
• mild allergic reaction*

* To learn more about this side effect, see the “Side effects of diltiazem in detail” section below.

Diltiazem ER oral capsule may cause more mild side effects than those listed above. For details, see the drug’s prescribing information.

Serious side effects of diltiazem

Diltiazem may cause certain serious side effects. If you have any serious side effects from diltiazem extended-release (ER) oral capsule, call your doctor right away. But if you think you’re having a medical emergency or your side effects feel life threatening, take immediate action. Call 911 or a local emergency number, or go to the nearest emergency room.

After the Food and Drug Administration (FDA) approves a drug, it tracks and reviews side effects of the medication. Visit MedWatch’s website if you’d like to notify the FDA about a side effect you’ve had with diltiazem.

Serious side effects of diltiazem ER oral capsule that occurred in studies include:

• hallucinations (seeing or hearing things that aren’t there)
• heart failure
• orthostatic hypotension (low blood pressure when sitting or standing up that may lead to fainting)
• severe skin reactions, including exfoliative dermatitis
• slow heart rate*
• heart block*
• liver damage*
• severe allergic reaction*

* To learn more about this side effect, see the “Side effects of diltiazem in detail” section below.

Common questions about side effects of diltiazem

Here are answers to some common questions about side effects of diltiazem extended-release (ER) oral capsule. If you have other questions, talk with your doctor or pharmacist.

How long do side effects of diltiazem take to go away?

It depends. Generally, most side effects caused by diltiazem are mild and go away within a few hours or days. In rare cases, side effects may last longer.

Talk with your doctor or pharmacist if you have side effects that don’t go away or bother you. They can review your symptoms and discuss the best way to treat them. This may involve stopping treatment with diltiazem.

Is diltiazem safe for older adults?

Yes, diltiazem is generally safe for older adults (ages 65 years and older). There are no known differences in the safety or efficacy of the drug in older adults compared with younger adults.

But as you age, your organs, including your heart, liver, and kidneys, may not work as well as they used to. Because of this, doctors may prescribe a lower starting dosage of diltiazem for older adults.

If you have questions about whether your health history and age affect how safe it’s for you to take diltiazem, talk with your doctor.

Does diltiazem cause long-term side effects?

Yes, in some cases, diltiazem ER oral capsule may cause long-term side effects. Examples of long-term side effects reported with diltiazem ER oral capsule include heart failure and heart block. (To learn more about heart block, see the “Side effects of diltiazem in detail” section below.)

These side effects can last for a while after you’ve stopped taking the drug.

Talk with your doctor to learn more about these side effects and how to manage them. Your doctor can tell how long these side effects of diltiazem may last.

Coupon for diltiazem

Visit this page to access Optum Perks coupons and get price estimates for diltiazem when you use the coupons. These coupons can provide significant savings on your prescription costs. 

Note: Optum Perks coupons cannot be used with insurance copays or benefits.

Side effects of diltiazem in detail

Below you’ll find details on some of the side effects of diltiazem extended-release (ER) oral capsule.

Slow heart rate

In studies, bradycardia (slow heart rate) was common in people taking diltiazem ER oral capsule. This side effect may be mild or serious. Serious bradycardia was rare, while mild slow heart rate was more common in studies.

With bradycardia, your heart rate is slower than usual. This condition doesn’t always cause symptoms. But it’s possible to experience fatigue (low energy), weakness, and shortness of breath from this side effect.

Certain factors can increase the risk of bradycardia with diltiazem ER oral capsule. These include taking a higher diltiazem dosage. It also includes taking the medications clonidine (Nexiclon XR, Kapvay) or ivabradine (Corlanor) together with diltiazem.

Ways to manage

If you experience symptoms of slow heart rate, tell your doctor. They’ll likely recommend lowering your diltiazem dosage. Or they may suggest stopping treatment and reviewing other treatments for your condition instead.

Heart block

In studies, heart block was rare in people taking diltiazem ER oral capsule. But this side effect may be serious.

With heart block, the electrical signals that control your heart are disrupted. This condition may not cause symptoms. But it’s also possible to experience symptoms such as:

• chest pain
• heart palpitations (feeling as if your heart is skipping beats)
• shortness of breath

Certain factors can increase the risk of heart block with diltiazem ER oral capsule. These include taking the following drugs with diltiazem: digoxin (Lanoxin) or a beta-blocker, such as metoprolol (Lopressor, Toprol XL).

Ways to manage

If your symptoms feel severe or life threatening, call 911 (or your local emergency number) or seek immediate medical attention. Severe heart block is considered a medical emergency. 

If you experience mild symptoms of heart block, tell your doctor. They’ll likely recommend lowering your diltiazem dosage. Or they may suggest stopping treatment and reviewing other treatments for your condition instead.

Liver damage

In studies, liver damage was rare in people taking diltiazem ER oral capsule. But this side effect may be serious.

With liver damage, your liver is harmed and doesn’t work as well as usual. Symptoms include:

• jaundice (yellowing of your skin or the whites of your eyes)
• pain in your abdomen
• swelling in your abdomen, legs, or ankles

This side effect is most likely to occur within the first 8 weeks after you start taking diltiazem. Liver damage caused by diltiazem tends to be reversible once treatment is stopped. 

Ways to manage

If you experience symptoms of liver damage, tell your doctor. They’ll likely recommend stopping treatment with diltiazem. They can also recommend treatment for your liver symptoms if needed.

Allergic reaction

For some people, diltiazem ER oral capsule can cause an allergic reaction. These reactions were rarely reported in studies of diltiazem, but they can occur.

Symptoms can be mild or serious, and they may include:

• itchiness
• skin rash
• swelling under the skin, usually affecting eyelids, lips, hands, or feet
• swelling of the mouth, tongue, or throat, which can make it hard to breathe
• flushing (temporary warmth, redness, or deepening of skin color)

Ways to manage

For mild allergic reaction symptoms, such as a mild rash, call your doctor right away. They may recommend treatments to help manage your symptoms. They’ll also let you know whether you should keep taking the medication.

For severe allergic reaction symptoms, such as swelling or trouble breathing, call 911 or your local emergency number right away. These symptoms require immediate medical care because they can become life threatening. If you’ve had a serious allergic reaction to diltiazem ER oral capsule, your doctor may recommend taking a different medication instead.

Warnings for diltiazem

Below are some factors you may want to discuss with your doctor before taking diltiazem extended-release (ER) oral capsule.

Warnings

It may not be safe for you to take diltiazem ER oral capsule if you have specific health conditions. These are sometimes called drug-condition interactions. Other things may also affect whether diltiazem ER oral capsule is a safe treatment option for you.

Before taking diltiazem ER oral capsule, tell your doctor about your health and medications you take. Things to consider include:

• sick sinus syndrome
• second– or third-degree heart block
• low blood pressure
• recent heart attack and congestion in your lungs
• Prinzmetal angina
• heart failure
• liver condition, such as liver cirrhosis
• past allergic reaction to diltiazem

Diltiazem and pregnancy

It’s not known whether diltiazem ER oral capsule should be taken during pregnancy. If you’re planning a pregnancy or can become pregnant, talk with your doctor before taking this medication.

Diltiazem and breastfeeding

Diltiazem ER oral capsule should not be taken while breastfeeding. If you’re currently breastfeeding or planning to do so, talk with your doctor before taking this medication. Your doctor may recommend other ways to feed your child during treatment with diltiazem.

Diltiazem and alcohol

Diltiazem ER oral capsule is known to interact with alcohol.

You should avoid drinking alcohol while taking diltiazem ER oral capsule. Alcohol can increase how quickly your body absorbs the drug. This raises your risk of side effects from diltiazem.

If you drink alcohol, talk with your doctor about whether other treatments besides diltiazem are a better option for you.

What to ask your doctor

This article describes common and serious side effects of diltiazem extended-release oral capsule. If your doctor prescribes this medication, they can discuss possible side effects with you. Let your doctor know if you have concerns or questions about treatment with this medication.

Here’s a list of some possible questions you may want to ask your doctor:

• How do side effects of diltiazem compare with other treatments for my condition?
• How will my liver health be monitored during treatment with diltiazem?
• Will taking other blood pressure medications with diltiazem raise my risk of side effects?

Disclaimer: Optum Perks has made every effort to make certain that all information is factually correct, comprehensive, and up to date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or another healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.