Epilepsy: seizure types and drug treatment

Epilepsy is a chronic brain disease with recurrent unprovoked seizures. Seizures are classified by where they start (focal, generalised or unknown onset) and by awareness and movement. The type of seizure guides drug choice, because focal and absence seizures arise from different circuits and respond to different mechanisms.

Seizure terminology and classification

• Focal aware: symptoms depend on the cortical area involved (jerking of a limb, tingling, a strange feeling), with awareness kept.
• Focal with impaired awareness: a brief loss of awareness, often with lip smacking or hand wringing.
• Focal to bilateral tonic-clonic: a focal seizure that spreads to both sides.
• Generalised absence: sudden staring and stopping of activity, typically lasting seconds, most common in children.
• Generalised tonic-clonic, myoclonic (brief jerks) and atonic (sudden loss of tone) seizures.
• Unknown onset: when the start cannot be determined (for example, an unwitnessed tonic-clonic seizure).

Mechanisms and causes

Focal seizures arise from a localised area of cortex where excitation outpaces inhibition. Generalised absence seizures come from rhythmic firing between the thalamus and cortex, driven by low-threshold T-type calcium currents in thalamic neurons; this is why ethosuximide, which reduces T-type currents, works for absence but not focal seizures. WHO groups causes as structural, genetic, infectious, metabolic, immune and unknown; about half of cases have no known cause. Brain infections such as neurocysticercosis (pork tapeworm larvae in the brain) are among the preventable causes. Many epilepsy-causing gene variants affect ion channels; for example, loss-of-function variants in SCN1A, which encodes the neuronal sodium channel Nav1.1, are found in infants with Dravet syndrome.

Choosing a drug by seizure type

• Focal seizures: lamotrigine, levetiracetam, carbamazepine, oxcarbazepine, lacosamide and others.
• Generalised tonic-clonic: valproate, lamotrigine or levetiracetam.
• Absence: ethosuximide or valproate (clonazepam is an alternative).
• Myoclonic: valproate, or levetiracetam as an add-on.
• Rare syndromes: cannabidiol and fenfluramine for Dravet syndrome; vigabatrin for infantile spasms (boxed warning for permanent visual field loss).
• Pregnancy potential: several antiseizure drugs are linked to birth defects, valproate most strongly. Under the stricter EU rules, valproate is not started in girls or women who could become pregnant unless alternatives are unsuitable and a pregnancy prevention programme is followed.

Treatment principles and duration

Treatment starts with one drug (monotherapy), increased gradually until seizures are controlled or side effects limit it; if it fails, another drug is substituted or added. Drug interactions matter: enzyme inducers such as carbamazepine and phenytoin speed the metabolism of many other drugs. After about two seizure-free years, slow tapering can be considered, weighing clinical, social and personal factors. WHO notes a large treatment gap in low- and middle-income countries, often because affordable generic antiseizure medicines are not available in public services.

Status epilepticus

A prolonged seizure or repeated seizures without recovery is a neurological emergency: the longer it lasts, the harder it is to stop and the greater the risk of brain injury. Treatment combines airway, breathing and circulation support with rapid drug therapy.

• First: a benzodiazepine. Intravenous lorazepam outperformed phenytoin alone in a large trial, and intramuscular midazolam was as effective as intravenous lorazepam, which suits treatment before hospital.
• Second: a longer-acting intravenous antiseizure drug, such as fosphenytoin, which is labelled for generalised tonic-clonic status epilepticus and usually given together with a benzodiazepine.
• Persisting seizures: intensive care, where breathing may need temporary support.
• Watch for breathing depression and low blood pressure from high doses of the drugs used.

Febrile and infant seizures

A small share of young children have a convulsion during a febrile illness, and a minority of them have another. Most febrile seizures are brief, do not harm the brain and are not epilepsy. The later risk of epilepsy is higher with a pre-existing neurological disorder or developmental delay, a family history of epilepsy, or a complicated febrile seizure (long, one-sided or followed by another the same day). Daily preventive antiseizure drugs were once common; for children at high risk, a rectal benzodiazepine given at the time of fever can prevent recurrences without the side effects of long-term therapy. Infantile spasms are a separate, severe epilepsy that responds poorly to the usual drugs; vigabatrin is one option.

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Example drugs

• Lamotrigine
• Levetiracetam
• Carbamazepine
• Valproic acid
• Ethosuximide
• Lorazepam
• Midazolam
• Fosphenytoin
• Vigabatrin
• Cannabidiol

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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, 2026); Valproate and related substances - referral | European Medicines Agency (EMA) (European Medicines Agency, 2026); DailyMed - FOSPHENYTOIN SODIUM injection, solution (DailyMed (U.S. National Library of Medicine), 2026).

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