Calcium Channel Blockers

Reviewed by: HU Medical Review Board | Last reviewed: April 2023

Calcium channel blockers are most often used to treat high blood pressure (hypertension). Some drugs in this class have been used to prevent migraine attacks, since they are easy to use and have few side effects.1

However, guidelines issued by the American Headache Society do not include calcium channel blockers in their table of treatments with evidence of effectiveness in preventing migraine. Instead, calcium channel blockers have been downgraded to a status (Level U) that states: “Evidence is conflicting or inadequate to support or refute the use of the following medications for migraine prevention.2,3

When they are used, calcium channel blockers can sometimes lose their effectiveness over time, but this can often be helped by taking higher doses or switching to a similar drug.1

How do calcium channel blockers work?

Calcium channel blockers (also called calcium antagonists) prevent calcium from entering cells of the heart and blood vessel walls. This helps prevent the muscles in the vessels from contracting and tightening. As a result, the blood vessels relax and widen, which leads to lower blood pressure. Some calcium channel blockers work more specifically on the heart muscle, and others work better on blood vessels.4


Commonly prescribed calcium channel blockers include:2

  • Nicardipine (Cardene®)
  • Nifedipine (Adalat®, Procardia®, Afeditab®)
  • Nimodipine
  • Verapamil (Calan® , Covera® , Verelan®)

What are the possible side effects?

The most common side effects of calcium channel blockers include:2,4

  • Constipation
  • Dizziness
  • Extreme tiredness
  • Fast heartbeat
  • Flushing
  • Headache
  • Low blood pressure
  • Nausea
  • Swelling in the legs and feet
  • Weight gain

These are not all the possible side effects of calcium channel blockers. Talk to your doctor about what to expect when taking calcium channel blockers. You also should call your doctor if you have any changes that concern you when taking calcium channel blockers.

Other things to know

Avoid grapefruit and grapefruit juice when taking the calcium channel blockers diltiazem and verapamil. Grapefruit reduces the liver’s ability to eliminate the drug from your system. This can affect your heart rate and blood pressure, and lead to headaches and dizziness.4

Before you begin calcium channel blockers, tell your doctor if:5

  • You are allergic to the medication
  • You have heart problems besides angina or high blood pressure
  • You are pregnant or breastfeeding
  • You have diabetes
  • You have liver problems

Before beginning treatment for migraine, tell your doctor about all your health conditions and any other drugs, vitamins, or supplements you are taking. This includes over-the-counter drugs.

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