Antiepileptic Medications - Part 1

Early antiepileptics (approved before 1990) include several medications that are still commonly used in epilepsy treatment.  Drug choice varies based on type of epilepsy and choice of individual agent is complex.  Many antiepileptics can be used for a variety of seizure disorders; however, certain drugs are only indicated in specific seizure disorders. For example, ethosuximide is only indicated in the treatment of absence seizures.  Antiepileptic choice must also take into account the patient's other medical conditions and age to determine the most appropriate medication.

Class Drugs

• Carbamazepine

• Divalproex

• Ethosuximide

• Phenobarbital

• Phenytoin

• Primidone

Class Mechanism of Action

• See each drug

Class Application

• Treatment of seizures

• Other applications apply to individual drugs

Class Adverse Effects

• See each drug

• Drug interactions are the norm and not the exception

• Pregnancy concerns

Many drugs cause birth defects or developmental problems such as neural tube defects, cognitive defects, and behavioral abnormalities

• Pregnancy planning is important

• Many drugs increase the metabolism of oral contraceptives

Phenytoin

• Phenobarbital

• Carbamazepine

Drug Table

Drug Name	Application	Comments	Image
Carbamazepine	Seizures; Trigeminal neuralgia; Bipolar disorder	Mechanism; -Sodium channel blocker; -Eliminates repetitive signals (action potentials) in the epileptic focus; Adverse Effects; -Erratic absorption causing varying blood levels; -Hyponatremia; -Do not use in absence seizures (may increase seizures); -Induces own metabolism; -Blood dyscrasias; -Stevens-Johnson syndrome	"Car" "Maze"
Divalproex	Seizures; Bipolar disorder; Headache	Mechanism; -Multiple possible mechanisms; -Sodium channel blockade; -GABA blockade; -Reduces ganglionic low threshold calcium current; Adverse Effects; -Teratogenic; -Hepatotoxic; -Pancreatitis	"Divide Sign" "Pro"
Ethosuximide	Absence seizures only	Mechanism; -Inhibition of T-type calcium channels; Adverse Effects; -SLE; -Abrupt discontinuation leads to seizures	"Ether" and "Sucking Vacuum"
Phenobarbital	Status epilepticus	Mechanism; Enhances GABA inhibition; Adverse Effects; -Impaired cognitive development in children; -Impaired cognitive function in adults; -Can precipitate acute intermittent porphyria by increasing porphyrin synthesis (induction of hepatic delta-aminolevulinic acid synthase)	"Fence" and "Barb"
Primidone	Status epilepticus	Mechanism; -Metabolized to phenobarbital; -Enhances GABA inhibition	"Prime Rib" "Done"
Phenytoin	Focal seizures; Tonic-clonic seizures; Status epilepticus	Mechanism; -Blocks Na channels in inactive state, slowing recovery; Adverse Effects; Rapid saturation kinetics; Small changes in dose can increase free drug levels quickly; -CNS depression; Cerebellum and vestibular system most affected; -Nystagmus; -Ataxia; -Gingival hyperplasia; -Peripheral neuropathy; -Osteoporosis	"Fence" "Toe"