11 Diltiazem Interactions You Should Know About
Key takeaways:
Diltiazem (Cardizem) is a medication used to treat high blood pressure and chest pain. It’s available as immediate- and extended-release capsules and tablets.
Diltiazem interacts with many medications. Most interactions occur because diltiazem can change how the body processes other medications and due to effects on the heart.
Always share your current medication list with your healthcare provider and pharmacist. They can help identify and manage potential medication interactions.
Table of contents
Diltiazem (Cardizem) is a popular medication used to manage high blood pressure and relieve angina (chest pain). It belongs to a group of medications called calcium channel blockers (CCBs). Along with other CCBs, diltiazem can interact with other medications you’re taking.
Medications that slow your heart rate are a common culprit. And medications processed by your liver can be affected, too. Many diltiazem interactions are expected and managed up front by your healthcare provider. But there are several important interactions you should know about.
1. Carbamazepine
Carbamazepine (Tegretol) is an antiepileptic medication used to treat seizures. It’s also taken to treat trigeminal neuralgia, a type of facial pain. Like many other antiepileptic medications, carbamazepine has lots of interactions.
When taken together, diltiazem can increase carbamazepine levels in the body. As a result, you may be more likely to experience side effects. This can include dizziness, drowsiness, and balance problems. In severe cases, coma and seizures are possible.
Your healthcare provider may need to monitor your blood work with this combination. If needed, they may adjust your carbamazepine dosage.
2. Clonidine
Clonidine (Catapres) is a medication used to treat high blood pressure. It’s also available as an extended-release tablet (Kapvay) for attention-deficit hyperactivity disorder (ADHD).
Both clonidine and diltiazem can slow down your heart rate. When taken together, your heart rate may slow down too much (called bradycardia). This can cause dizziness, irregular heartbeat, and/or extreme tiredness. In severe cases, hospitalization may be required.
Your healthcare provider may want to closely monitor your heart rate during treatment. Keep in mind it may not be obvious that your heart rate is too low without taking your pulse. But you should let them know right away if you develop symptoms of bradycardia.
3. Cyclosporine
Cyclosporine (Sandimmune) and cyclosporine modified (Neoral, Gengraf) are immunosuppressant medications. They’re used to prevent organ transplant rejection. Cyclosporine modified is also used to treat certain autoimmune conditions.
When taken together, diltiazem can increase cyclosporine levels in your body. This can increase the likelihood of kidney or liver problems.
Cyclosporine requires regular blood tests to ensure your dosage is safe and effective. Your healthcare provider may conduct blood tests more often with this combination. This is important when starting, adjusting, or stopping diltiazem.
Your transplant team will ensure medications you’re taking are compatible with your transplant regimen. If needed, your cyclosporine dosage can be adjusted if your levels are too high.
4. Digoxin
Digoxin (Lanoxin) is a medication that helps manage heart failure and heart rhythm problems. Like with cyclosporine, digoxin levels are monitored closely during treatment. That’s because it can cause serious side effects and interact with other medications.
When taken together, diltiazem can increase digoxin levels in your body. This can increase the likelihood of side effects and digoxin toxicity. Most commonly, side effects include nausea, vomiting, and diarrhea. Vision changes are also possible.
Digoxin toxicity can become life-threatening. Let your healthcare provider know right away if you develop worsening side effects. Seek immediate medical attention if they feel severe or include irregular heartbeats or fainting.
Your healthcare provider will monitor your digoxin levels during treatment. They may check more often when starting, adjusting, or stopping diltiazem. If necessary, they can adjust your digoxin dosage.
5. Certain statin medications
If you have high cholesterol, you’re likely familiar with statins. They’re first-choice medications to help lower cholesterol. And they can lower the risk of heart attack and stroke in certain people, too. Some statins are known to interact with diltiazem. These include simvastatin (Zocor), lovastatin, and atorvastatin (Lipitor).
When taken together, diltiazem increases the levels of these statins in your body. This can increase the risk of statin-related side effects, like muscle pain or damage. Your healthcare provider may opt for a different statin that doesn’t interact.
If not, they may need to lower your statin dose. For example, the FDA recommends limiting your simvastatin dosage to 10 mg daily if you’re also taking diltiazem. Let your healthcare provider know if you develop muscle pain with this combination.
6. Ivabradine
Ivabradine (Corlanor) is a medication that helps keep you out of the hospital if you have heart failure. Like diltiazem, it lowers your heart rate. But it doesn’t affect your blood pressure.
When taken with diltiazem, your heart rate may slow down too much. And diltiazem can cause higher levels of ivabradine in your body, too. This can put you at risk of bradycardia and serious heart rhythm problems. This combination should be avoided.
7. Quinidine
Quinidine is an older medication used to treat and prevent heart rhythm problems. It’s not used as often since it has many side effects and interactions.
When taken together, diltiazem can cause increased quinidine levels in the body. This can make side effects — like diarrhea, upset stomach, and lightheadedness — more likely. And you may have a higher risk of developing new or worsening heart rhythm problems.
You may be prescribed a different heart rhythm medication if you’re taking diltiazem. But if you need to take them together, pay close attention to how you feel. Tell your healthcare provider if you’re experiencing new or worsening side effects. They may need to adjust your quinidine dosage with this combination.
Seek immediate medical attention if you develop chest discomfort, fast heartbeat, or fainting,
8. Rifampin
Rifampin is an antibiotic used to treat tuberculosis and prevent meningococcal disease transmission. It can interact with many medications, including diltiazem.
When taken together, rifampin significantly lowers the amount of diltiazem in the body. This can prevent diltiazem from working as well as it should. For that reason, this combination should be avoided.
9. Cimetidine
Cimetidine (Tagamet) is an over-the-counter medication used to prevent and treat heartburn. It’s also available as a prescription product for gastroesophageal reflux disease (GERD) and a few other conditions. Like rifampin, cimetidine has many interactions.
When taken with diltiazem, cimetidine can affect how it’s broken down by your liver. This can result in higher diltiazem levels than usual, increasing the likelihood of side effects.
Luckily, there are many other treatment options available for heartburn. So, your healthcare provider may recommend a safer alternative. Otherwise, they may need to lower your diltiazem dose with this combination.
10. Beta blockers
Beta blockers are a class of medications used to treat conditions like high blood pressure, heart failure, and heart rhythm problems. Some are also used off-label for migraine prevention and performance anxiety. Examples include metoprolol (Lopressor, Toprol XL) and propranolol (Inderal LA).
Like diltiazem, beta blockers slow down your heart rate. Some people can take this combination without issues. But there are reports suggesting that it may be dangerous for others. What’s more, diltiazem may increase propranolol levels, too.
Your healthcare provider will determine if this combination is right for your specific situation.
11. Alcohol
It’s generally a good idea to minimize or avoid alcohol while taking blood pressure medications. That’s because you may be more likely to experience side effects. And it may prevent your medications from controlling your blood pressure as well.
But CCBs, like diltiazem, can interact with alcohol in several additional ways. For example, this combination can cause alcohol to be removed from your body more slowly. This can make you feel “drunker” for longer and put you at higher risk of alcohol poisoning.
Diltiazem is available as immediate- and extended-release (ER) tablets and capsules. Alcohol can cause the ER capsules to release more quickly in the body. This may cause your body to absorb more diltiazem, leading to higher levels.
Because of these reasons, it’s best to avoid alcohol when taking diltiazem. However, you may be wondering if one or two drinks are OK while taking it. Talk to your healthcare provider about how much alcohol is safe to drink during treatment.
When should I contact my healthcare provider about a diltiazem interaction?
If you’re ever concerned about a diltiazem interaction, contact your healthcare provider. They’re likely already aware of the interaction. But it never hurts to check. Your pharmacist can also be a great resource for potential interactions.
Let your healthcare provider know if you develop new or worsening side effects or symptoms during treatment. The same goes for readings that are higher than normal if you’re monitoring your blood pressure at home. This could be a sign that your medications need to be adjusted.
Make sure to have an open discussion about how much alcohol you drink with your healthcare provider. They can advise how much you can safely drink while taking diltiazem.
The bottom line
Diltiazem interacts with many medications by changing the way the body processes them. Other interactions can result in additive effects, like slower heart rate.
Your healthcare provider and your pharmacist can help identify potential interactions. Some interactions can be avoided with safer alternatives. Others can be managed by adjusting your medications.
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References
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Jain, A., et al. (2022). Quinidine. StatPearls.
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PD-Rx Pharmaceuticals, Inc. (2022). Cimetidine [package insert].
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Tapia, C., et al. (2021). Cyclosporine. StatPearls.
U.S. Food & Drug Administration. (2017). FDA drug safety communication: New restrictions, contradictions, and dose limitations for Zocor (simvastatin) to reduce the rise of muscle injury.
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