Ethosuximide
A succinimide antiepileptic for absence (petit mal) seizures, as in childhood absence epilepsy; UK labels also cover myoclonic seizures.
Drug card
- Class
- Succinimide
- How it works
- Blocking T-type calcium channels in the thalamus to stop absence seizures
- Used for
- Absence (petit mal) seizures
- Myoclonic seizures (UK license)
- Known for
- Nausea, vomiting and abdominal pain
- Stevens-Johnson syndrome, TEN and DRESS
Study it as a flashcard, and it comes back before you forget it.
Mechanism of action
How does ethosuximide work?
Ethosuximide probably works by partly blocking T-type calcium channels in thalamic neurons, which cuts the burst firing behind absence seizures and suppresses their 3-per-second spike-and-wave EEG pattern. It is more specific for pure absence seizures than other antiepileptics, and its plasma half-life is more than 24 hours.
Uses
What is ethosuximide used for?
- Absence (petit mal) seizures
- Myoclonic seizures (UK license)
Side effects
Side effects of ethosuximide
- Nausea, vomiting and abdominal painKnown for
- Stevens-Johnson syndrome, TEN and DRESSKnown forSerious
- Loss of appetite and weight loss
- Drowsiness and tiredness
- Headache and hiccups
- Dizziness and unsteadiness (ataxia)
- Psychosis, depression and night terrorsSerious
- Agranulocytosis, pancytopenia and aplastic anemiaSerious
- Immune thrombocytopenia (very low platelets)Serious
- Drug-induced lupusSerious
- Gum overgrowth and swollen tongue
- Excess body hair (hirsutism)
Known for marks what an exam expects you to know it for.
Watch for
Cautions and what sets it apart
- Blood counts are checked regularly; sore throat, fever or bleeding needs an urgent count.
- Used alone in mixed epilepsy it may increase tonic-clonic seizures, and stopping suddenly can bring on absence status.
- It is contraindicated in porphyria (UK); it can raise phenytoin levels, and valproate can raise or lower its levels.
- It crosses the placenta and into breast milk; birth defects have been reported, so the benefit is weighed in pregnancy.
Good to know: In a large childhood absence epilepsy trial, ethosuximide and valproate controlled seizures better than lamotrigine, and ethosuximide caused fewer attention problems than valproate.
Remember it
A way to remember it
Two Ts: T-type channels in the thalamus.
Succinimides block T-type calcium channels in thalamic neurons, which pace the 3-per-second spike-and-wave rhythm of absence seizures; that is why absence epilepsy is their main use.
Written for biofideX
Its class
Succinimides
Succinimides are thought to block T-type calcium channels in thalamic neurons. These channels drive the rhythmic burst firing of thalamocortical circuits that produces the 3-per-second spike-and-wave pattern of absence seizures, so blocking them suppresses that pattern and raises the seizure threshold. Used alone in mixed epilepsy, they can let tonic-clonic seizures increase.
Easily mixed up with valproate and sodium channel-blocking antiepileptics.
Sources
Checked against
Written for biofideX in plain words, after checking these references:
- Ethosuximide capsules: label (DailyMed)
- Ethosuximide 250 mg capsules: SmPC (emc)
- Ethosuximide (NCI Thesaurus)
- Ethosuximide (WHO eEML)
For learning pharmacology, not for treatment decisions: no doses are given, and a prescriber, pharmacist or the product's own label is the word on any one patient. Spotted a mistake? Tell us and we'll correct it.
Epilepsy and nerve pain
Ethosuximide is one of 8 drugs practiced together here: their classes, how they work, what they treat and what they're known for.
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