9 Diltiazem Side Effects and How to Manage Them

Diltiazem is a medication used to treat high blood pressure and chest pain. It belongs to a class of medications called calcium channel blockers and goes by many brand names, including Cardiazem, Tiazac, and Cartia XT. Because of how it works, diltiazem can cause unpleasant side effects such as constipation, swelling, and dizziness.

Some diltiazem side effects can be temporary and lessen over time as your body adjusts to the medication. But others, like low blood pressure and heart rate, are important to keep in mind — especially if your dosage is adjusted or other medications are added to your regimen.

Below, we cover nine potential diltiazem side effects, how to manage them, and when to contact your healthcare provider about them.

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1. Headache

Like other calcium channel blockers, diltiazem can cause headaches. This may be due to blood pressure changes from the medication. Often, this side effect subsides over time as your body adjusts to the treatment. 

But if headaches start interfering with your daily activities or don’t go away, let your healthcare provider know. It’s possible that they’re from diltiazem — or something else, such as hormonal changes. Your provider can help pinpoint the cause and suggest next steps.

2. Dizziness

You may feel dizzy while taking diltiazem, especially as you’re getting started with the treatment. Dizziness can also happen if your blood pressure drops too low.

You may be more likely to feel dizzy when changing positions too quickly, such as going from sitting to standing. Try changing positions more slowly to allow your body time to adjust. And if you don’t feel steady on your feet, sit or lie back down. This can help you avoid falling.

If your dizziness is starting to interfere with your daily activities, let your healthcare provider know. It’s possible that your dosage needs to be adjusted, or the medication may need to be stopped. But if you experience dizziness with fainting, chest pain, or irregular heartbeat, go to the nearest emergency room.

3. Constipation

Diltiazem can cause constipation, which is a common calcium channel blocker side effect. If you become constipated, there are a few things you can do to get things moving again. Examples include keeping hydrated, exercising regularly, and introducing more fiber into your diet. 

If needed, your pharmacist can also recommend an over-the-counter (OTC) laxative that’s safe with other medications you’re taking. They can also tell you how long you can potentially take it for. But if nothing seems to be helping, let your healthcare provider know. They may adjust your dosage or recommend an alternative that’s less likely to cause constipation.

4. Swelling

Diltiazem can cause swelling (edema) in your legs and ankles. This is more common with other calcium channel blockers, like amlodipine. But it’s still possible with diltiazem, especially with higher doses and long-term use.

There are a few things you can do to help lessen leg swelling during treatment. Wearing compression socks or elevating your legs according to your healthcare provider’s instructions are a few examples. If this doesn’t seem to help, your provider may try lowering your dose.

5. Stuffy nose

Diltiazem can cause nasal congestion in some people. Thankfully, this side effect can easily be managed in most cases. For example, using a saline spray three to four times a day can help improve your stuffy nose. You can also use a vaporizer or inhale steam two to four times a day.

Your pharmacist can also recommend some OTC decongestants. However, it’s important to know that some decongestants are not recommended for people with high blood pressure. Plus, using nasal sprays longer than 3 days can make your stuffy nose worse.

6. Low blood pressure

Since diltiazem can lower your blood pressure, there’s a chance you may experience hypotension when taking it. This is when your blood pressure drops too low. The risk of hypotension increases if you combine diltiazem with other blood pressure medications.

If your blood pressure drops too low, you may experience symptoms such as blurred vision, dizziness and lightheadedness, and weakness. Let your healthcare provider know if this happens, since they may need to lower your dose. Get immediate medical attention if your symptoms feel severe or life-threatening.

7. Slow heart rate

Diltiazem works by slowing your heart rate to lessen the workload on your heart. Sometimes, this may cause your heart rate to slow down too much (called bradycardia), especially as your dose increases.

A slow heart rate isn’t always cause for concern. But if you develop symptoms such as excessive fatigue or shortness of breath, let your healthcare provider know. This could indicate that your diltiazem dose is too high.

8. Liver problems

Some people may have changes on their liver tests while taking diltiazem, which can be a sign of liver inflammation or damage. Usually, this is temporary and doesn’t cause any noticeable symptoms. Your healthcare provider may monitor these tests during routine follow-ups.

While rare, symptomatic liver problems have been reported in people taking calcium channel blockers like diltiazem. This risk may be higher if you take diltiazem with other medications that can cause liver damage, such as statins.

If you start experiencing symptoms of liver problems such as fever, rash, or jaundice (yellowing of the skin and eyes), inform your healthcare provider.

9. Worsening heart failure

Experts recommend that people with certain types of heart failure avoid calcium channel blockers like diltiazem since it can worsen symptoms without any benefits.

If you have pre-existing heart failure, or if you develop heart failure while taking diltiazem, make sure your healthcare provider is aware. They can determine the best next steps and treatment options for you.

When should you contact your healthcare provider about diltiazem side effects?

Many diltiazem side effects are mild and should gradually improve as your body gets used to the medication. But if they start interfering with your daily functioning or seem to be getting worse, contact your healthcare provider.

Some side effects can be more serious, such as very low blood pressure or heart rate. If your blood pressure or heart rate is dropping too low, your diltiazem dosage may be too high. Your healthcare provider may decide to lower it, but don’t attempt to do this on your own.

If any symptoms you’re experiencing feel severe or life-threatening, go to the nearest emergency room. This may include chest pain, irregular heartbeat, or passing out.

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Written by:

Sandy P. Bonfin, PharmD, BCPS

Sandy Bonfin has 9 years of experience as a pharmacist and has been working as a clinical pharmacist in a hospital in Florida for the past 7 years after a short stint as a mail-order retail pharmacist. Sandy has worked in pediatric medicine, emergency medicine, internal medicine, and intensive care.

Edited by:

Alyssa Billingsley, PharmD

Alyssa Billingsley, PharmD, is the director of pharmacy content for GoodRx. She has over a decade of experience as a pharmacist and has worked in clinical, academic, and administrative roles.

Reviewed by:

Joshua Murdock, PharmD, BCBBS

Joshua Murdock, PharmD, BCBBS, is a licensed pharmacist in Arizona, Colorado, and Rhode Island. He has worked in the pharmacy industry for more than 10 years and currently serves as a pharmacy editor for GoodRx.

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