Antiepileptics
Also known as: antiepileptic drugs, anticonvulsants, aeds
Antiepileptics are medications that prevent or reduce seizures by dampening abnormal electrical activity in the brain. They work mainly by blocking sodium or calcium channels, enhancing GABA inhibition, or reducing glutamate excitation.
Antiepileptic drugs, also called anticonvulsants, control seizures by shifting the balance between excitation and inhibition in neurons. Three broad mechanisms cover most agents. Sodium channel blockers — phenytoin, carbamazepine, oxcarbazepine, lamotrigine — slow the recovery of voltage-gated sodium channels and limit high-frequency firing. GABA enhancers — phenobarbital, benzodiazepines such as diazepam and lorazepam, and to a degree valproic acid — increase inhibitory chloride conductance. Calcium channel blockers such as ethosuximide act on T-type channels in the thalamus, which is why ethosuximide is the drug of choice for absence seizures. Several agents, including valproic acid, topiramate, and levetiracetam, act by more than one mechanism.
Selection depends on seizure type and patient factors. Broad-spectrum agents such as valproic acid, lamotrigine, and levetiracetam cover multiple seizure types, while narrow-spectrum drugs are matched to focal or absence seizures. Benzodiazepines are the first-line rescue treatment for status epilepticus because of their rapid onset. Many antiepileptics are also used off-label or by approved indication for neuropathic pain, migraine prophylaxis, and bipolar disorder — carbamazepine, valproic acid, and lamotrigine all serve as mood stabilizers, and gabapentin and pregabalin are used mainly for neuropathic pain.
Pharmacy technicians should recognize several safety themes. Phenytoin, carbamazepine, and valproic acid have narrow therapeutic indexes and require serum level monitoring. Carbamazepine and phenytoin induce hepatic CYP enzymes, accelerating the metabolism of many other drugs including oral contraceptives, while valproic acid is an enzyme inhibitor. Valproic acid and several others are teratogenic and carry pregnancy warnings. Lamotrigine requires slow titration to reduce the risk of severe rash, and carbamazepine carries a boxed warning for serious dermatologic reactions and blood dyscrasias. Abrupt discontinuation of any antiepileptic can precipitate seizures.
The PTCE covers antiepileptics in its medications-by-organ-system content for the nervous system, grouped with antipsychotics and lithium. Expect to match brand and generic names, identify indication and drug class, and flag agents that require therapeutic monitoring or carry boxed warnings.
Key takeaways
- Antiepileptics reduce seizures by blocking sodium or calcium channels, enhancing GABA, or reducing glutamate activity.
- Ethosuximide blocks thalamic T-type calcium channels and is used for absence seizures.
- Benzodiazepines are the rapid-onset first-line treatment for status epilepticus.
- Phenytoin, carbamazepine, and valproic acid have narrow therapeutic indexes and require serum monitoring.
- Many antiepileptics are also used for neuropathic pain, migraine prevention, and bipolar disorder.