Antiseizure medication selection and retention for adult onset focal epilepsy in a Swedish health service region: A population-based cohort study.

Objective: Historically, approximately half of those with newly diagnosed epilepsy have responded to and tolerated the first antiseizure medication (ASM), but there are few contemporary real-world data. Third-generation ASMs have improved tolerability and are increasingly used according to prescription data. We aimed to describe current ASM selection and retention in adult onset focal epilepsy in western Sweden.

Methods: A multicenter retrospective cohort study was performed at five public neurology care providers in western Sweden (nearly complete coverage in the area). We reviewed 2607 medical charts and included patients diagnosed with nongeneralized epilepsy after January 1, 2020 who had a seizure onset after age 25 years (presumed focal onset) and were started on ASM monotherapy.

Results: A total of 542 patients (median age at seizure onset = 68 years, interquartile range = 52-77) were included. Most patients received levetiracetam (62%) or lamotrigine (35%), with levetiracetam being more common among men and those with structural causes or short epilepsy duration. During follow-up (median = 471.5 days), 463 patients (85%) remained on the first ASM. Fifty-nine (18%) patients discontinued levetiracetam, and 18 (10%) ended treatment with lamotrigine (p = .010), most commonly because of side effects. In a multivariable Cox regression model, the discontinuation risk was higher for levetiracetam than lamotrigine (adjusted hazard ratio = 2.01, 95% confidence interval = 1.16-3.51).

Significance: Levetiracetam and lamotrigine were the dominating first ASMs for adult onset focal epilepsy in our region, indicating good awareness of problems with enzyme induction or teratogenicity of older drugs. The most striking finding is the high retention rates, perhaps reflecting a shift toward an older epilepsy population, higher tolerability of newer ASMs, or suboptimal follow-up. The finding that treatment retention differed among patients receiving levetiracetam and lamotrigine aligns with the recent SANAD II results. It suggests lamotrigine may be underutilized in our region and that education efforts are needed to ensure it is considered the first choice more often.