Sodium Channel Blockers

Epilepsy is a brain disease that causes people to have seizures. With epilepsy, nerve cells in the brain, called neurons, 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.

Dozens of anti-seizure drugs may be prescribed for epilepsy. One type is sodium channel blockers. These drugs do not cure epilepsy but change how abnormal electrical activity affects the brain. This helps stop or reduce seizures.^1,2

Sodium channel blockers are some of the most common and best-understood drugs prescribed for epilepsy. This is a large group of drugs. Some medicines in this drug class are prescribed for only 1 or 2 types of seizures. Depending on the type of seizure, these drugs may be prescribed for:³

• Generalized seizures
• Focal seizures
• Absence seizures
• Status epilepticus
• Myoclonic seizures
• Tonic/atonic seizures
• Lennox-Gastaut syndrome
• Childhood epilepsy syndromes

How do sodium channel blockers work?

Neurons are connected by wire-like structures called axons which allow neurons to communicate with each other. These axons 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

Sodium channel blockers work as the name says: They block pathways opened by too many electrical signals. Because epilepsy seizures are caused by nerve cells over-firing, slowing or blocking the sodium channel leads to fewer seizures.¹

Examples

Drugs in this class of anti-seizure medicines include:^1,3,4

• Carbamazepine (Epitol^®, Tegretol^®, Carnexiv™, Equetro^®, and Teril^®)
• Carbamazepine-XR (Carbatrol^® and Tegretol^®-XR)
• Cenobamate (Xcopri^®)
• Eslicarbazepine Acetate (Aptiom^®)
• Ethotoin (Peganone^®)
• Fosphenytoin (Cerebyx)
• Lacosamide (Vimpat^®)
• Lamotrigine (Lamictal)
• Oxcarbazepine (Oxtellar XR^® and Trileptal^®)
• Phenytoin (Dilantin^®, Epanutin^®, and Phenytek^®)
• Rufinamide (Banzel^® and Inovelon^®)
• Zonisamide (Zonegran^®)

Some sodium channel blockers have been prescribed for epilepsy for years. For example:^1,3,4

• Phenytoin has been used since 1938
• Carbamazepine was approved for epilepsy in 1974
• Valproate was approved for epilepsy in 1978
• Topiramate was approved for epilepsy in 1996

What are the possible side effects?

Side effects are common with any type of anti-seizure medicine. Side effects can vary depending on the specific drug you are taking. The most common side effects of sodium channel blockers include:^3,4

• Dizziness
• Nausea and vomiting
• Problems with coordination, balance, and speech
• Double vision
• Blurred vision
• Blood disorders like anemia
• Rash or itching
• Headaches
• Vitamin deficiencies
• Hormone imbalances
• Osteoporosis (bone loss)
• Changes in heart rhythm and blood pressure
• Weight gain or weight loss
• Fatigue and sleepiness
• Insomnia
• Hair loss
• Tremor
• Brain fog or confusion
• Suicidal thoughts
• Low levels of salt in the blood (hyponatremia)

This is a large group of drugs, and some 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 sodium 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 sodium channel blockers.

Things to know about sodium channel blockers

Your doctor will routinely test your blood to monitor your blood counts of red blood cells, white blood cells, platelets, liver, and kidney function. All seizure drugs can cause problems with how the bone marrow and organs work. Regular blood work helps your doctor control side effects.⁴

Depending on the drug, you may take these medicines by mouth, by injection, by infusion, or by mouth, as pills or syrup. Some can be taken with other anti-seizure medicines, while others can only be taken alone.³

Some of these drugs should not be taken during pregnancy due to the possibility of birth defects or while breastfeeding. Others may make birth control pills less effective.³

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

• Calcium channel blockers
• Slowing (inhibitory) transmitters
• Extra (excitatory) transmitters
• SV2A protein binders
• Other types

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.