What are calcium channel blockers?

Calcium channel blockers (CCBs) are a class of medications used to treat high blood pressure. They’re also called calcium antagonists. They’re as effective as ACE inhibitors in reducing blood pressure.

Your doctor may prescribe CCBs if you have:

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

High blood pressure can also be treated with other forms of medication. Your doctor may prescribe both a CCB and another hypertensive drug at the same time.

The newest guidelines from the American College of Cardiology recommend that ACE inhibitors, diuretics, angiotensin-receptor blockers (ARBs), and CCBs be the first medications to consider when treating high blood pressure. Certain groups of people may especially benefit from CCBs in combination with other medications, including:

  • African-Americans
  • individuals with kidney disease
  • the elderly
  • people with diabetes

CCBs reduce blood pressure by limiting the amount of calcium or the rate at which calcium flows into the heart muscle and arterial cell walls. Calcium stimulates the heart to contract more forcefully. When calcium flow is limited, 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.

CCBs are available in a number of oral formats, ranging from short-acting dissolving tablets to extended-release capsules. The dosage will depend on your overall health and medical history. Your doctor will also 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.

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

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

Because of their action, dihydropyridines are more commonly used to treat hypertension than other classes. 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

Other commonly prescribed CCBs used to treat angina and irregular heartbeats are verapamil (Verelan) and diltiazem (Cardizem CD).

CCBs may interact with other drugs or supplements you take. Make sure your doctor has an updated list of all of your medications, vitamins, and herbal supplements.

CCBs and grapefruit products, including whole fruit and juice, shouldn’t be taken together. Grapefruit products interfere with the normal excretion of the medication. It could be potentially dangerous if large amounts of the drug accumulate in your body. Wait at least four hours after you’ve taken your medication before drinking grapefruit juice or eating grapefruit.

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

Some CCBs can 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 are prolonged, uncomfortable, or pose a threat to your health.

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 animal studies, magnesium supplementation seemed to be most effective in the young with elevated blood pressure, before they developed hypertension. It also seemed 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 if eating foods high in magnesium will affect the potency of the CCBs you’re taking.