Calcium Channel Blockers

Reviewed by: HU Medical Review Board | Last reviewed: November 2023 | Last updated: November 2023

Epilepsy is a brain disease that causes people to have seizures. With epilepsy, neurons (nerve cells in the brain) do not work properly. Neurons normally create tiny electrical signals in a highly-regulated rhythm. These signals tell other parts of the brain and body what to do.

During a seizure, neurons create too many electrical signals, too quickly. Some doctors describe this as an electrical storm in the brain.

There are dozens of anti-seizure drugs that may be prescribed for epilepsy. One type is calcium channel blockers. These drugs do not cure epilepsy but helps limit abnormal electrical activity in the brain. This helps stop or reduce seizures.1-4

Depending on the type of seizure, these drugs may be prescribed for:3,4

  • Absence seizures
  • Focal seizures (partial seizures)
  • Generalized seizures

How do calcium channel blockers work?

Neurons have a membrane, or cover, with many pathways that block or allow charged particles, or ions, to pass through. These pathways are called channels. The flow of charged particles through these channels creates the electrical activity of nerve cells. Many of these nerve cell channels also open and close based on the electrical activity of the nerve. This important role means these channels help control the firing (excitation) and slowing (inhibition) of nerve signals in the brain.2

There are 3 types of calcium channels in neurons in the brain. These channels help regulate electrical signals in the brain, often promoting neuron firing. Because epilepsy seizures are caused by nerve cells over-firing, slowing or blocking the calcium channel can lead to fewer seizures.1-4


Drugs in this class of anti-seizure medicines include:4-6

  • Ethosuximide (Zarontin®)
  • Gabapentin (Neurontin® and Fanatrex™)
  • Methsuximide (Celontin®)
  • Pregabalin (Lyrica®)
  • Valproate (Depakote®)
  • Zonisamide (Zonegran®)

What are the possible side effects?

Side effects are common with any anti-seizure medicine. Side effects can vary depending on the specific drug you are taking. The most common side effects of calcium channel blockers include:4-6

  • Nausea, vomiting, diarrhea, constipation, or stomach pain
  • Sleep problems
  • Swelling
  • Rash
  • Sleepiness
  • Hyperactivity
  • Dizziness
  • Weight gain or weight loss
  • Problems with coordination, balance, or speech
  • Confusion and brain fog
  • Blurred vision
  • Sensitivity to light
  • Suicidal thoughts

Some of the medicines in this drug class may cause a few of these side effects but not others. None of these drugs cause all of these symptoms. Sometimes side effects can be reduced by lowering the dose or switching to a different drug.

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

Things to know about calcium channel blockers

Many of these medications require some monitoring with blood work. Depending on which medication, your doctor will test your blood to monitor things such as liver or kidney function, the electrolytes or salts in your blood, or your blood counts of red blood cells, white blood cells, and platelets. Some seizure drugs can cause problems with how the bone marrow and organs work. Regular blood work helps your doctor monitor for side effects.5

Sometimes your doctor may recommend combining 2 or more anti-seizure medicines, often from different classes.3,5

Some of these drugs should not be taken during pregnancy due to the possibility of birth defects. Doctors do not know if whether some of these drugs are safe to take while pregnant or breastfeeding. Discuss with your doctor if you are planning on becoming pregnant.5

Other types of anti-seizure medicines work on different pathways. These include:

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

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