Relative Seizure Relapse Risks Associated with Antiepileptic Drug Withdrawal After Different Seizure-Free Periods in Adults with Focal Epilepsy: A Prospective, Controlled Follow-Up Study

Abstract

Approximately two-thirds of patients with newly diagnosed epilepsy become seizure-free after antiepileptic drug (AED) treatment. A crucial issue for these patients and their families, especially after a long period of seizure freedom, is when to stop their medications. The aim of this study was to identify the optimal timing of AED withdrawal inadults with focal epilepsy who had been seizure-free for ≥ 2years. Adults with focal epilepsy who had been seizure-free for ≥ 2years were recruited. Based on their decision to discontinue (withdrawal) or continue (non-withdrawal) AED treatment, patients were assigned to withdrawal or non-withdrawal subgroups according to the length of remission (2 to < 3years, 3 to < 4years, 4 to < 5years and ≥ 5years). The relapse risks of the withdrawal and corresponding non-withdrawal subgroups were compared, and the relative relapse risks were assessed in a Cox proportional hazard regression model. A total of 213 eligible patients began to withdraw from AED treatment; 70 had been seizure-free for 2 to < 3years, 62 had been seizure-free for 3 to < 4years, 37 had been seizure-free for 4 to < 5years and 44 had been seizure-free for ≥ 5years. The figures for the corresponding non-withdrawal subgroups were 463, 334, 251 and 182, respectively. There was a significantly higher risk of seizure relapse in patients withdrawing from AEDs after 2 to < 5years of seizure freedom than in the corresponding non-withdrawal controls, and the relative relapse risk was 3.052 (95% confidence interval [CI] 2.126-4.381; p < 0.001) for the seizure-free period of 2 to < 3 years, 3.617 (95% CI2.384-5.488; p < 0.001) for 3 to < 4years and 2.644 (95% CI 1.456-4.799; p = 0.001) for 4 to < 5years. However, for patients who were seizure-free for ≥ 5years, AED withdrawal did not significantly increase the risk of seizure relapse compared with that of patients continuing treatment (hazard ratio [HR] 1.362, 95% CI 0.634-2.926, p = 0.428). Compared with a seizure-free period of 2 to < 3years, the relative relapse risk after AED withdrawal was significantly reduced only after being seizure-free for ≥ 5years (HR 0.441, 95% CI 0.233-0.834; p = 0.012). Overall, for adults with focal epilepsy, withdrawal from AEDs significantly increased the risk of seizure relapse after being seizure-free for 2 to < 5years, but might not increase the risk if the seizure-free period was ≥ 5years.