Pharmacokinetic Study With an Oral Suspension of Perampanel as Adjunctive Therapy in Pediatric Subjects With Epilepsy

This is a multicenter, open-label study comprised of pretreatment, treatment (core study), and extension phases that is designed to evaluate the PK of an oral suspension of perampanel (maximum dose must not exceed 12 milligrams per day \[mg /day\] for participants taking non-enzyme-inducing antiepileptic drug \[non-EIAED\] or 16 mg/day for participants taking EIAED) when given as an adjunctive therapy in participants ranging from 1 month to less than 4 years of age with epilepsy. The Pretreatment Phase will last up to 2 weeks, during which participants will be assessed for their eligibility to participate in the study. The Treatment Phase will consist of 3 periods: Titration (12 \[for participants taking non-EIAED\] to 16 weeks \[for participants taking EIAED\]), Maintenance (4 weeks), and Follow-Up (4 weeks; only for those participants who complete the Maintenance Period but do not continue into the Extension Phase and those participants who discontinue study participation). Extension Phase: The Extension Phase will consist of 2 periods: Maintenance (32 weeks \[for participants taking EIAED\]; 36 weeks \[for participants taking non-EIAED\]) and Follow-Up (4 weeks). The maximum total duration of treatment for each participant will be 52 weeks and the maximum total duration of the study for each participant will be 58 weeks (2 weeks Pretreatment+52 weeks of treatment+4 weeks Follow-up).