To compare the 12-month retention rate, effectiveness and tolerability of perampanel (PER) as a first or late add-on treatment in adult patients with focal-onset seizures (FOS), including focal to bilateral tonic-clonic seizures (FBTCS).
This retrospective, observational, multicenter study was carried out in patients with FOS that received PER as a late add-on (n = 60), after failure of > 3 AEDs, and a group that received PER as a first add-on treatment (n = 21).
At 12 months, the retention (90.5 % vs. 48.3 %; p = 0.001), seizure-freedom (71.4 % vs. 13.3 %; p < 0.001) and responder (85.7 % vs. 28.3 %; p < 0.001) rates were significantly higher in the first add-on group compared with the late add-on group. In patients with FBTCS, the 12-month retention rate did not differ significantly between the first and late add-on groups (93.8 % vs. 66.7 %); however, seizure-freedom (81.2 % vs. 27.8 %; p = 0.002) and responder rate response (93.8 % vs. 44.4 %; p = 0.002) were significantly higher in the first add-on group. There were no significant differences in tolerability between the two groups, including in patients with FBTCS. Adverse events were reported in 54.3 % of patients (44/81), most were mild or moderate, with dizziness being the most frequent one.
Overall, retention rate and effectiveness at 12 months were significantly higher in patients taking PER as a first add-on than as a late add-on, and the tolerability of PER did not differ significantly between groups. PER demonstrated high effectiveness in patients with FBTCS, even as a late add-on treatment.

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