Calcium channel blockers (CCBs) are a class of medications used to treat high blood pressure (hypertension). They work by blocking some of the calcium that enters the heart and arteries.

You may have heard of calcium as a key nutrient for your bones, but it also plays a very important role in heart function. Calcium moves into the cells of your heart every time it beats, allowing a strong and even squeeze of the muscles to happen.

If you have high blood pressure, the force of blood flowing through your arteries is higher than normal. Taking CCBs works by reducing the flow of calcium into your heart and arteries, which helps to:

  • lower blood pressure
  • open narrow blood vessels
  • reduce heart rate

CCBs are also sometimes called calcium antagonists. They’re as effective as ACE inhibitors in reducing blood pressure.

CCBs are available in many forms that you take by mouth, ranging from short-acting dissolving tablets to extended-release capsules. The dosage will depend on your overall health and medical history.

Your doctor may prescribe CCBs if you have:

  • high blood pressure
  • irregular heartbeats called arrhythmias
  • chest pain related to angina

Other forms of medication can also treat high blood pressure. Your doctor may prescribe both a CCB and another hypertensive drug at the same time.

The 2017 guidelines from the American College of Cardiology recommend the following medications be considered first when treating high blood pressure:

  • ACE inhibitors
  • diuretics
  • angiotensin-receptor blockers (ARBs)
  • CCBs

Certain groups of people may especially benefit from CCBs in combination with other medications, including:

  • older adults
  • Black people
  • people with kidney disease or diabetes

Side effects of CCBs include:

  • dizziness
  • headache
  • constipation
  • heartburn
  • nausea
  • a skin rash or flushing, which is redness of the face
  • swelling in the lower extremities
  • fatigue

Certain CCBs can also lower blood glucose levels in some people.

Tell your doctor about any side effects you’re experiencing. They may adjust your dosage or recommend that you switch to another medication if the side effects don’t go away, are uncomfortable, or pose a threat to your health.

Your doctor will take your age into consideration before prescribing a blood pressure-lowering medication. CCBs are often less likely to cause side effects in people over the age of 65.

CCBs reduce blood pressure by limiting the amount of calcium that flows into heart muscle and arterial cell walls.

Calcium particles help create the electrical signal that makes the heart contract, or beat. With less calcium flowing into the muscles and arteries, your heart’s contractions aren’t as strong with each beat, and your blood vessels are able to relax. This leads to lower blood pressure.

The three main subclasses of CCB drugs are based on their chemical structure and activity:

  • Dihydropyridines work mostly on the arteries.
  • Benzothiazepines work on the heart muscle and arteries.
  • Phenylalkylamines work mostly on the heart muscle.


Because of the way they work in the body, dihydropyridines are more commonly used to treat hypertension than other subclasses of CCBs. This is due to their ability to reduce arterial pressure and vascular resistance.

Dihydropyridine calcium antagonists usually end in the suffix “-pine” and include:

  • amlodipine (Norvasc)
  • felodipine (Plendil)
  • isradipine
  • nicardipine (Cardene)
  • nifedipine (Adalat CC)
  • nimodipine (Nymalize)
  • nitrendipine


Benzothiazepines and phenylalkylamines fall under a grouping of CCBs called nondihydropyridines. These drugs lower blood pressure but also have other effects on the heart. They’re generally used to treat angina (chest pain) and arrhythmia (irregular heartbeat).

Verapamil (Verelan) is one commonly prescribed phenylalkylamine.

Diltiazem (Cardizem CD) is one example of a benzothiazepine.

Natural calcium channel blockers

Magnesium is an example of a nutrient that acts as a natural CCB.

Research has shown that higher levels of magnesium block the movement of calcium in the body.

In animal studies, magnesium supplementation seemed to be most effective in treating young animals with elevated blood pressure, before they developed hypertension. It also seemed to slow the progression to hypertension.

Magnesium-rich foods include:

  • brown rice
  • almonds
  • peanuts
  • cashews
  • oat bran
  • shredded wheat cereal
  • soy
  • black beans
  • bananas
  • spinach
  • avocado

Ask your doctor whether eating foods high in magnesium will change the effects of the CCBs you’re taking.


CCBs may interact with other drugs you take, making them less effective or increasing the likelihood of side effects. These include:

  • treatments for heart conditions, including ACE inhibitors, statins, and antiarrhythmic drugs
  • antiretroviral therapies
  • antiseizure drugs
  • corticosteroids
  • cyclosporine
  • digitalis
  • diuretics

Taking CCBs should also be avoided in people with mental health conditions who experience orthostatic hypotension due to their medications.

Orthostatic hypotension is a type of low blood pressure that happens when you move from sitting or lying down to standing up. It’s a common side effect of antipsychotic medications.

Food and alcohol

It’s generally recommended to avoid drinking alcohol, especially binge drinking, when taking blood pressure medication.

You should also avoid taking CCBs and consuming grapefruit products, including whole fruit and juice, at the same time.

Grapefruit products interfere with your body’s normal process for getting rid of the CCBs, which could be potentially dangerous if large amounts of the drug build up in your body.

Wait at least 4 hours after you’ve taken your medication before drinking grapefruit juice or eating grapefruit.


Certain supplements may increase or decrease the effectiveness of CCBs. These include:

  • calcium or vitamin D in large doses
  • fumitory
  • ginkgo extract
  • hawthorn
  • khella
  • lily of the valley
  • night-blooming cereus

CCBs are some of the first medications considered for people with high blood pressure, especially older adults.

They’re generally considered a safe and effective drug. Serious side effects are rare with CCBs.

If you’ve been prescribed a CCB, try learning about the possible side effects and drug interactions. Report these to your doctor if you experience any symptoms. Be sure to provide your doctor with an updated list of all of your medications, vitamins, and herbal supplements.