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 inhibitory transmitters. These drugs do not cure epilepsy but change how abnormal electrical activity affects 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 membranes, or covers, with many pathways that block or allow chemicals 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 brain signals.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®)
- Clorazepate (Tranxene®)
- Diazepam nasal (Valtoco®)
- Diazepam rectal (Diastat®)
- Diazepam tablets (Valium®)
- Midazolam nasal (Nayzilam®)
- Midazolam injection (Seizalam®)
- 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®)
Clobazam (Onfi®, Sympazan®) is an inhibitory transmitter sold outside the United States.
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
- Slowed heartbeat or breathing
- Brain fog, confusion, or problems concentrating
- Problems with coordination, balance, or speech
- Decreased sex drive
- 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
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.3
Depending on the drug, you may take these medicines by mouth, nasal spray, suppository, injection, or infusion. Some can be taken with other anti-seizure medicines, while others can only be taken alone.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:
- Sodium channel blockers
- Calcium channel blockers
- SV2A protein binding
- Other types such as extra (excitatory) transmission
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.