Antiseizure medications: mechanisms, pharmacokinetics and adverse effects
How antiseizure medications act on sodium channels, GABA, SV2A, calcium channels and glutamate, why phenytoin and carbamazepine behave unpredictably, the inducer and inhibitor interactions examiners test, HLA-linked hypersensitivity, and teratogenic risk including current valproate advice.
Tier 1Medical sciences concept
Written with AI assistance and fact-checked against the sources below. For exam study, not clinical decisions. How notes are made
At a glance
- Antiseizure medications (ASMs) reduce excitation (sodium channels, calcium channels, glutamate release) or increase inhibition (GABA). Many act at several targets.
- Match mechanism to seizure type: sodium channel blockers suit focal epilepsy but can worsen absence and myoclonic seizures.
- Phenytoin has saturable (zero-order) metabolism, so small dose changes cause large level changes. Carbamazepine induces its own metabolism.
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Sources
- Therapeutic Guidelines: NeurologyAU/NZTherapeutic Guidelines Ltd, 2026
- Australian Medicines HandbookAU/NZAustralian Medicines Handbook Pty Ltd, 2026
- Sodium valproate: balancing benefits and risks especially in people of childbearing potentialAU/NZAustralian Prescriber (McLaughlin, 2026;49:84-7), 2026
- Comparative risk of major congenital malformations with eight different antiepileptic drugs: a prospective cohort study of the EURAP registryLancet Neurology (Tomson et al., 2018;17:530-8), 2018
- Clinical Pharmacogenetics Implementation Consortium guideline for HLA genotype and use of carbamazepine and oxcarbazepine: 2017 updateClinical Pharmacology and Therapeutics (Phillips et al., 2018;103:574-81), 2018
- Clinical Pharmacogenetics Implementation Consortium (CPIC) guideline for CYP2C9 and HLA-B genotypes and phenytoin dosing: 2020 updateClinical Pharmacology and Therapeutics (Karnes et al., 2021;109:302-9), 2020
- ILAE classification of the epilepsies: position paper of the ILAE Commission for Classification and TerminologyEpilepsia (Scheffer et al., 2017;58:512-21), 2017
- Last updated
- 14 November 2026
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