Class Explorer · Neurology
Antiseizure medications
Reduce neuronal excitability by blocking sodium channels, enhancing GABA, or modulating synaptic vesicle release. Choice is driven as much by interactions, pregnancy and monitoring burden as by efficacy.
Members
LevetiracetamNo interactions, no levels, and sometimes a personality change.PhenytoinThe drug where dose and concentration stop being proportional.Valproate (valproic acid, divalproex)Broad-spectrum, highly effective, and the most teratogenic drug in common use.CarbamazepineInduces its own metabolism, and everyone else's.
Also in this class: Lamotrigine · Topiramate · Lacosamide. Full pages arrive as the library grows.
Compare the members
Levetiracetam
- Kinetics
- Linear, renal
- Interactions
- Essentially none
- Levels
- Not routine
Phenytoin
- Kinetics
- Zero-order past saturation
- Interactions
- Potent inducer
- Levels
- Yes, corrected for albumin
Valproate (valproic acid, divalproex)
- Kinetics
- Non-linear protein binding
- Interactions
- Inhibitor
- Levels
- Yes
Carbamazepine
- Kinetics
- Auto-induction over weeks
- Interactions
- Potent inducer
- Levels
- Yes
Shared across the class
- Indications
- Epilepsy · Some agents: bipolar disorder, neuropathic pain, migraine prophylaxis
- Adverse effects
- Sedation, dizziness, ataxia · Rash, occasionally severe · Teratogenicity
- Contraindications
- Agent-specific; valproate in pregnancy is the hardest line in the class
- Monitoring
- Seizure frequency, which is the actual endpoint · Levels only where they mean something: phenytoin, carbamazepine, valproate · CBC and liver enzymes for valproate and carbamazepine · Sodium for carbamazepine · Mood and behaviour for levetiracetam
What makes each agent different
- Levetiracetam has essentially no interactions and needs no levels, which is why it has become the ward default; its cost is behavioural, with irritability and mood change in a meaningful minority.
- Phenytoin has zero-order kinetics: past saturation, a small dose rise produces a large level rise. It is the classic drug where dose and concentration part company.
- Carbamazepine induces its own metabolism and everyone else's, and carries the HLA-B*1502 risk of severe cutaneous reaction in patients of Han Chinese and South-East Asian ancestry.
- Valproate is highly effective and highly teratogenic; it is not prescribed to anyone who could become pregnant without a documented pregnancy-prevention discussion.
A phenytoin level must be interpreted against albumin: the assay reports total drug, and it is the free fraction that acts.
Never switch an epileptic patient between manufacturers casually; small bioavailability differences have precipitated breakthrough seizures.
Last reviewed 2026-08-16 · Goodman & Gilman's The Pharmacological Basis of Therapeutics, 14th ed.