Calcium Channel Blockers

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 steady 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 change how abnormal electrical activity affects 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. Nerve cell channels are meant to open and close based on the electrical activity they normally receive. This important role means the channels 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. Think of them as the pacemaker of normal brain activity. Because epilepsy seizures are caused by nerve cells over-firing, slowing or blocking the calcium channel leads 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

Your doctor will test your blood on a schedule to monitor your blood counts of red blood cells, white blood cells, and platelets. All seizure drugs can cause problems with how the bone marrow and organs work. Regular blood work helps your doctor control side effects.5

Some of these drugs can be taken with other anti-seizure medicines, while others can only be taken alone.3,5

Doctors do not know if these drugs are safe to take while pregnant or breastfeeding.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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Written by: Jessica Johns Pool │Last reviewed: November 2021