Inhibitory Transmitters

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 inhibitory transmitters. These drugs do not cure epilepsy but limit abnormal electrical activity in the brain. This helps stop or reduce seizures.1,2

Inhibitory transmitters are a large group of drugs and some of the oldest used to treat epilepsy. Some medicines in this drug class are prescribed for only 1 or 2 types of seizures. Some are taken alone to control seizures, while others are added to other anti-seizure drugs. These drugs may be prescribed for:2

  • Myoclonic seizures
  • Generalized seizures
  • Drug-resistant epilepsy
  • Status epilepticus
  • Breakthrough seizures, including seizure clusters
  • Focal onset seizures
  • Absence seizures
  • Photosensitive epilepsy
  • Lennox-Gastaut syndrome

How do inhibitory transmitters 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.1,2

Inhibit means to stop or slow something. Neurotransmitters are chemical messengers in the brain. GABA (gamma amino butyric acid) is a neurotransmitter that works by inhibiting, or suppressing, neurons. This causes the neurons to calm down and fire less. Anti-seizure drugs that target GABA work by increasing the inhibitory effect in the brain. This reduces the firing of neurons and leads to fewer seizures.1,2


Drugs in this class of anti-seizure medicines include:3

  • Cannabidiol (CBD) oral solution (Epidiolex)
  • Clonazepam (Epitril™, Klonopin®, Rivotril®)
  • Clobazam (Onfi®, Sympazan®)
  • Clorazepate (Tranxene®)
  • Diazepam nasal (Valtoco®)
  • Diazepam rectal (Diastat®)
  • Diazepam tablets (Valium®)
  • Midazolam nasal (Nayzilam®)
  • Midazolam injection (Seizalam®)
  • Phenobarbital
  • Primidone (Mysoline®)
  • Stiripentol (Diacomit®)
  • Tiagabine hydrochloride (Gabitril®)
  • Divalproex Sodium (Depacon®, Depakote®, Epival®, Valproate sodium® (IV))
  • Divalproex sodium-ER (Depakote ER®)
  • Valproic acid (Convulex®, Depakene®, Depakine®, Orfiril®, Stavzor®, Valporal®, Valprosid®)
  • Vigabatrin (Sabril® and Vigadrone®)

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 inhibitory transmitters include:2

  • Sleepiness and fatigue
  • Restlessness, irritability, or hyperactivity
  • Depression
  • Slowed heartbeat or breathing
  • Brain fog, confusion, or problems concentrating
  • Problems with coordination, balance, or speech
  • Decreased sex drive
  • Dizziness
  • Headache
  • Nausea, vomiting, diarrhea, or stomach pain
  • Birth defects

This is a large group of drugs, and none cause all of these symptoms. Sometimes side effects can be reduced by lowering the dose or switching to a different drug. Stopping some of these drugs suddenly can cause different side effects, like fast heartbeat or breathing and tremor.3

These are not all the possible side effects of inhibitory transmitters. 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 inhibitory transmitters.

Things to know about inhibitory transmitters

Some 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.3

Depending on the drug, you may take these medicines by mouth, nasal spray, suppository, injection, or infusion. Sometimes your doctor may recommend combining 2 or more anti-seizure medicines, often from different classes.2

While this class of drugs may work well for certain types of seizures, many interact poorly with other medicines. Also, the drowsiness these drugs cause may limit how much, or how often, someone can take these medicines.2

Some of these drugs may not be safe to take while pregnant or breastfeeding.

Other types of anti-seizure medicines work on different pathways and 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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Treatment results and side effects can vary from person to person. This treatment information is not meant to replace professional medical advice. Talk to your doctor about what to expect before starting and while taking any treatment.