Long-term efficacy and safety of perampanel as a first add-on therapy in patients with focal epilepsy: Three-year extension study

•The 50% responder rate was 84.8% during the 3rd year and 71.7% during the 3 years.•The seizure-free rate was 58.7% during the 3rd year and 32.6% during the 3 years.•The 1-, 2-, and 3-year retention rates were 62.5%, 53.1%, and 52.1%, respectively.•Efficacies were higher in patients receiving ≤4 mg of perampanel.•No new safety signals were identified during the long-term follow-up period.