The Phase II and Phase III clinical development program of perampanel is providing a wealth of data on the safety and tolerability of this alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor antagonist as an adjuvant treatment for refractory partial-onset seizures. In Phase II dose-finding studies, perampanel was associated with an acceptable tolerability profile up to the maximum evaluated dose of 12 mg/day. Subsequent multinational, multicenter, randomized, double-blind, placebo-controlled Phase III registration studies further supported the tolerability of perampanel across the dose range 2–12 mg/day, with interim data from ongoing extension studies indicating that safety outcomes may be maintained over several years. An analysis of the pooled Phase III data indicated that the frequency of adverse events reported with perampanel generally increased in a dose-dependent manner, and the most common adverse events were dizziness and somnolence. Overall, perampanel has been associated with an acceptable and consistent safety profile that is maintained over long-term settings.