Calcium Channel Blockers Drug Interactions

Instructor: Justine Fritzel

Justine has been a Registered Nurse for 10 years and has a Bachelor's of Science in Nursing degree.

Calcium channel blockers are a class of prescription drugs. As with all medications, there are numerous potential drug interactions that can occur. In this lesson, we will review some of those drug interactions.

What are Calcium Channel Blockers?

Calcium channel blockers are a class of prescription medications that are used to treat hypertension or high blood pressure, coronary artery disease, and angina or chest pain.

They work by blocking the tiny channels that allow calcium to enter the cells. When calcium enters the cell the muscles contracts. By blocking the calcium, the muscle relaxes. When the blood vessels relax, they widen and result in decreased blood pressure. This also improves blood flow to the heart muscle.

There are several medications that are calcium channel blockers. Amlodipine, nifedipine, and verapamil are all calcium channel blocker medications. Before starting a calcium channel blocker, you need to be aware of possible drug interactions. Let's learn more about these.

Drug Interactions

Any time you take more than one medication, you are at risk for having drug interactions. These can vary from minor to major interactions. It is important to review all of your medications with your physician and pharmacist when starting a new medication. Not only do you want to tell them about your prescription medications, but all over the counter medications, herbal or natural remedies, and vitamins and supplements that you are taking.

We will look specifically at drug interactions with specific calcium channel blockers but the following are some general interactions for calcium channel blockers you should be aware of. If you are taking large amounts of Vitamin D or calcium supplements this may alter how effective your medication will be. If you are taking any other medications for the heart such as digitalis, blood pressure medications, or diuretics (water pills), this can cause a drug interaction with calcium channel blockers.

Certain eye medications (drops) can also result in drug interactions. When used with a calcium channel blocker they can increase the risk of low blood pressure and other heart issues. Examples of these medications are timolol and betaxolol ophthalmic solutions.

Corticosteroids in combination with a calcium channel blocker cause increased levels of corticosteroids and increase the likelihood of adverse effects.

Grapefruit juice interacts with many medications including calcium channel blockers and should be avoided.


If you are taking the calcium channel blocker, Verapamil, there are over 700 identified drug interactions. Of these, 123 are major, 530 moderate, and 49 minor.

If you are taking atorvastatin for high cholesterol, verapamil may increase the levels of atorvastatin. This is considered a moderate drug interaction. Atenolol is used for high blood pressure and when taken with verapamil puts you at higher risk of side effects. This is a major drug interaction.


Amlodipine is another calcium channel blocker that has nearly 600 listed drug interactions. There are 16 major, over 500 moderate, and 64 minor interactions identified.

Taking the antibiotic clarithromycin while taking amlodipine results in increased levels of amlodipine and puts you at high risk for low blood pressure and other adverse effects and should be monitored closely. If you take simvastatin with amlodipine, it is a major drug interaction as it could increase the levels of simvastatin.

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