Treatment outcome after failure of a first antiepileptic drug

Objectives: We assessed the likelihood of 12-month seizure remission and treatment failure after failure of a first antiepileptic drug, and identified factors influencing these outcomes.

Methods: SANAD (Standard and New Antiepileptic Drug) was a randomized controlled trial comparing monotherapy with standard and new antiepileptic drugs. Patients were followed up to study completion, even if they were switched from their randomized treatment. After a first treatment failure, we assessed the probability of 12-month seizure remission and treatment failure. Prognostic modeling identified predictors of these outcomes.

Results: Forty-four percent of patients in the SANAD trial had a first treatment failure. Seventy-five percent of these subsequently achieved 12-month remission by 6 years of follow-up. Significant prognostic factors included sex, age at treatment failure, time on randomized treatment at treatment failure, neurologic insult, total number of tonic-clonic seizures at treatment failure, reason for treatment failure, seizure type, and CT/MRI scan result. After a first treatment failure, young patients without tonic-clonic seizures, with a normal CT/MRI scan and failing their treatment because of unacceptable adverse events, had the highest likelihood of 12-month remission. Approximately 50% of patients who failed a first treatment also failed their second. Significant prognostic factors included total number of tonic-clonic seizures at first treatment failure, reason for first treatment failure, and CT/MRI scan result. Patients with tonic-clonic seizures and failing because of inadequate seizure control had the highest risk of a second treatment failure.

Conclusions: A high proportion of patients will achieve 12-month remission after a first treatment failure. Clinical factors can stratify patients according to likely outcome.