Pharmacology · Class
Antiseizure medicines !
Medicines that calm overexcited brain circuits so seizures stop or happen less often. Most people with epilepsy can become seizure free with them.
Updated 2026-11-01
What they are
The medicines used to prevent and treat epileptic seizures, also called antiepileptic drugs. According to WHO, up to 70% of people with epilepsy could become seizure free with appropriate use, yet many in low- and middle-income countries go untreated. In Latin America neurocysticercosis is an important, preventable cause of epilepsy.
Mechanism of action
Each drug tips the balance between excitation and inhibition in the brain. Some hold sodium channels in their inactive state (carbamazepine, phenytoin, lamotrigine, lacosamide); some block T-type calcium channels in the thalamus (ethosuximide); some strengthen GABA inhibition (phenobarbital, clobazam, tiagabine, vigabatrin); levetiracetam binds the synaptic vesicle protein SV2A; valproate and topiramate act on several targets at once.
Target: Voltage-gated sodium and calcium channels, GABA-A receptors, GABA metabolism and transport, SV2A
Drugs in this class
- CarbamazepineAn antiseizure medicine that also treats trigeminal neuralgia. It blocks sodium channels and, in some people of Asian…Voltage-gated sodium channel (Nav)
- Valproic acidA broad-spectrum antiseizure and mood-stabilizing medicine. It is the most teratogenic of its class and can damage the…Several targets: sodium channels, T-type calcium channels, GABA levels and histone deacetylases
- PhenytoinAn old, inexpensive sodium channel blocker for seizures. Its levels rise steeply with small dose changes, and long use…Voltage-gated sodium channel (Nav)
- LamotrigineA broad-spectrum antiseizure medicine and bipolar mood stabilizer. It is started very slowly because it can cause a…Voltage-gated sodium channel (Nav)
- LevetiracetamA widely used antiseizure medicine with few drug interactions. It binds a synaptic vesicle protein and can cause…Synaptic vesicle glycoprotein 2A (SV2A)
- PhenobarbitalThe oldest antiseizure medicine still in wide use, a barbiturate on the WHO essential list. It sedates, induces liver…GABA-A receptor (α1β2γ2)
- EthosuximideA medicine for absence seizures, the brief staring spells of childhood. It blocks T-type calcium channels in the…T-type calcium channel (Cav3)
- TopiramateAn antiseizure and migraine-prevention medicine with several targets. It causes weight loss, tingling, slowed thinking…Several targets; the figure shows carbonic anhydrase II
- FosphenytoinA water-soluble prodrug of phenytoin for intravenous or intramuscular use in status epilepticus. Infusing it too fast…Voltage-gated sodium channel (Nav), through phenytoin
- LacosamideA sodium channel antiseizure medicine that enhances slow inactivation. It can lengthen the PR interval of the ECG and…Voltage-gated sodium channel (Nav)
- OxcarbazepineA relative of carbamazepine for focal seizures. Its active metabolite blocks sodium channels; low blood sodium is its…Voltage-gated sodium channel (Nav)
- ClobazamA 1,5-benzodiazepine used as add-on treatment for Lennox-Gastaut syndrome. It sedates and, with opioids, can stop…GABA-A receptor, benzodiazepine site
- FelbamateA last-resort antiseizure medicine for severe epilepsy. It can cause aplastic anaemia and liver failure, so it is used…NMDA receptor, glycine site (GluN1)
- TiagabineAn add-on medicine for focal seizures that blocks the GABA transporter GAT-1, so GABA stays longer in the synapse.GABA transporter 1 (GAT-1)
- VigabatrinAn irreversible inhibitor of the enzyme that breaks down GABA, used for infantile spasms and refractory focal…GABA transaminase (GABA-T)
- ZonisamideA sulfonamide antiseizure medicine with a very long half-life. It blocks sodium and T-type calcium channels and…Voltage-gated sodium channels and T-type calcium channels
Others in the class
- Brivaracetam
- Eslicarbazepine
- Perampanel
- Cenobamate
- Rufinamide
- Primidone
- Clonazepam
Test yourself
Think of the answer, then tap the question to see it.
Which two medicines are first choices for typical absence seizures?
Ethosuximide and valproate. Both reduce the T-type calcium current of thalamic neurons that drives the 3-per-second spike-and-wave pattern.
Which antiseizure medicine carries the highest risk of neural tube defects?
Valproate. It also lowers IQ in exposed children, so it is avoided in pregnancy and in women of childbearing potential whenever an alternative works.
Why do enzyme-inducing antiseizure medicines matter for a woman using the pill?
Carbamazepine, phenytoin and phenobarbital speed up the breakdown of hormonal contraceptives, so contraception can fail.
Which genetic test is done before carbamazepine in people of Asian ancestry, and why?
HLA-B*1502. Carriers have a much higher risk of Stevens-Johnson syndrome and toxic epidermal necrolysis.
Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: Epilepsy (World Health Organization, 2024); Goodman & Gilman's The Pharmacological Basis of Therapeutics, 14th ed., ch. 20 (McGraw Hill, 2023); eEML - Electronic Essential Medicines List (World Health Organization, 2025); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026).
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Representative model, for educational purposes only.