Medication Summary
Early posttraumatic seizure (PTS) is treated with various antiepileptic drugs (AEDs). In most cases, administering the medication via the intravenous (IV) route is desirable, as the patient is still in the recovery stage from the head injury; phenytoin or fosphenytoin is the drug of choice for IV administration for acute seizures.
No evidence suggests that antiepileptic drugs (AEDs) influence the incidence of late PTS; therefore, prophylaxis has no place in caring for patients with head injuries. However, AEDs are effective in patients who develop posttraumatic epilepsy (PTE). The main drugs used for PTE are valproate and carbamazepine.
Also see Antiepileptic Drugs.
Anticonvulsants
Class Summary
These agents prevent seizure recurrence and terminate clinical and electrical seizure activity.
Sodium valproate (Depakote, Depakene, Depacon, Stavzor)
Valproate is chemically unrelated to other antiseizure drugs. Its mechanism of action has not been established; it may be related to increased brain levels of gamma-aminobutyric acid (GABA) or to enhanced GABA action. Valproate may potentiate postsynaptic GABA responses, affect the potassium channel, or have a direct membrane-stabilizing effect.
For conversion to monotherapy, the concomitant AED dose is ordinarily reduced by about 25% every 2 weeks. Reduction may start with therapy or delayed 1-2 weeks if seizures are possible with reduction; closely monitor patients during this time for increased seizure frequency.
As adjunctive therapy, valproate may be added to the regimen at 10-15 mg/kg/d. The dosage may increase by 5-10 mg/kg/wk for optimal clinical response. Optimal clinical response is usually achieved at a dose of less than 60 mg/kg/d.
Carbamazepine (Tegretol, Carbatrol, Equetro, Epitol)
Carbamazepine is indicated for complex partial seizures. It may block posttetanic potentiation by reducing summation of temporal stimulation. After therapeutic response, the dose can be reduced to the minimum effective level, or discontinued at least once every 3 months.
Phenytoin (Dilantin, Phenytek)
Phenytoin may act in the motor cortex, inhibiting spread of seizure activity; it may inhibit activity of brainstem centers responsible for the tonic phase of grand mal seizures.
Dosages must be individualized. Administer a larger dose before sleep if the dose cannot be divided equally. To minimize GI irritation, administer with or immediately after meals. Rapid injection or direct IV injection may cause severe hypotension or CNS depression.
Topiramate (Topamax)
Topiramate is a sulfamate-substituted monosaccharide with a broad spectrum of antiepileptic activity that may have state-dependent sodium channel blocking action, potentiating the inhibitory activity of the neurotransmitter gamma-aminobutyrate (GABA). It may block glutamate activity.
Levetiracetam (Keppra)
Levetiracetam is used as adjunctive therapy for partial seizures and myoclonic seizures. It is also indicated for primary generalized tonic-clonic seizures. Its mechanism of action is unknown.
