What is the recommended treatment for an adult with newly diagnosed absence seizures?

Adult-Onset Absence Seizures: Treatment Recommendations

For adults with newly diagnosed absence seizures, valproate is the first-line treatment, with lamotrigine as an alternative if valproate is contraindicated (particularly in women of childbearing potential). 1, 2

First-Line Treatment: Valproate

Valproate controls absence seizures in 75% of patients and is the drug of choice for this seizure type. 2 The medication also provides coverage against generalized tonic-clonic seizures (70% control rate) and myoclonic jerks (75% control rate), making it ideal for patients who may have multiple generalized seizure types. 2

Dosing Protocol for Valproate

• Start at 10-15 mg/kg/day and increase by 5-10 mg/kg/week until optimal clinical response is achieved. 1
• Optimal response typically occurs at daily doses below 60 mg/kg/day, with therapeutic plasma levels of 50-100 μg/mL. 1
• If total daily dose exceeds 250 mg, divide into multiple doses throughout the day. 1
• Monitor for thrombocytopenia risk, which increases significantly at trough levels above 110 μg/mL in females and 135 μg/mL in males. 1

Monitoring Requirements

• Obtain baseline liver function tests and blood counts before initiating therapy. 3
• Perform regular monitoring of liver function and complete blood counts during treatment, as toxic effects may be serious. 3
• Check fasting serum drug levels, especially when combining with other antiepileptic drugs, as interactions are pronounced. 3

Alternative First-Line: Lamotrigine

Lamotrigine may control absences in 50-60% of patients and is particularly useful when valproate is contraindicated. 2 This agent is especially important for women of childbearing potential, as valproate carries significantly increased risks of fetal malformations and neurodevelopmental delay. 4

Lamotrigine Considerations

• Lamotrigine is effective against both absence seizures and generalized tonic-clonic seizures, with typical and atypical absence seizures being particularly responsive. 5
• The major limitation is that lamotrigine may worsen myoclonic jerks if present. 2
• Skin rash occurs in approximately 10% of patients and is the most common cause of treatment withdrawal. 5
• Use a low, slow dosage titration schedule to minimize rash risk. 5

Second-Line: Ethosuximide

Ethosuximide controls 70% of absence seizures but is unsuitable as monotherapy if other generalized seizures coexist. 2 This agent should be reserved for patients with pure absence epilepsy who cannot tolerate valproate or lamotrigine. 2

Combination Therapy for Refractory Cases

If monotherapy fails, combine valproate with lamotrigine or ethosuximide. 2

• Low doses of lamotrigine added to valproate may have a dramatic beneficial effect in resistant cases. 2
• Clonazepam is particularly useful for absences with myoclonic components. 2
• Acetazolamide may serve as an adjunctive agent. 2

Critical Pitfalls to Avoid

• Never use carbamazepine as first-line therapy for absence seizures—it is ineffective for this seizure type and may worsen generalized epilepsy. 6
• Avoid valproate in women of childbearing potential unless no other options exist, due to teratogenicity risks. 4
• Do not exceed 60 mg/kg/day of valproate without careful consideration, as thrombocytopenia risk increases substantially. 1
• Ensure proper dosage titration with lamotrigine to minimize severe rash risk. 5

Special Considerations for Adult-Onset Absence Seizures

Adult-onset absence seizures occur in 10-15% of adults with epilepsy and may be combined with other generalized seizure types. 2 Unlike childhood absence epilepsy, adult-onset cases may represent different syndromic contexts requiring broader seizure coverage. 2

• Confirm diagnosis with video-EEG showing characteristic 3-4 Hz generalized spike-wave discharges. 2
• Test for seizure precipitation with hyperventilation, which triggers absences in 90% of untreated patients. 2
• Assess for other generalized seizure types (tonic-clonic, myoclonic) that would influence drug selection. 2
• Monitor for absence status epilepticus, which occurs in approximately 30% of patients with absence seizures. 2