Pooled data from 3 randomized clinical trials of ESL in patients with focal seizures (N=1447) were analyzed. After an 8-week baseline, patients were titrated over 2 weeks to their maintenance dose (400, 800, or 1200 mg/day; 12 weeks). Efficacy was assessed in a patient subset with ≥1 baseline FBTCS and ≥800 mg/day ESL maintenance dose by comparing standardized seizure frequency (SSF, FBTCS/28 day) during the maintenance period with placebo. Adverse events (AEs) were collected and tabulated.

A total 438 patients, aged 16-69, met the subset criteria and 429 patients had ≥1 post-baseline seizure diary entry. Baseline characteristics were balanced among treatment groups. Baseline median FBTCS SSF was 2.5 (placebo), 2.5 (ESL 800mg), and 2.4 (ESL 1200mg). During maintenance, the FBTCS SSF was lower in ESL groups (800mg, 0.9; 1200mg, 0.8) compared to placebo (1.1), and was significant for ESL 1200mg (P=0.0395, ANCOVA). ESL 1200mg patients achieved ≥50% reduction in SSF (61.9%, P=0.005, Cochran-Mantel-Haenszel test) or ≥75% reduction in SSF (46.0%, P=0.0315) at greater rates versus placebo (≥50%, 45.6%; ≥75%, 33.3%). Time to first seizure was significantly longer in ESL groups than placebo (Kaplan-Meier). Incidence of AEs and AEs leading to discontinuation increased with ESL dose. 

Adjunctive ESL was well-tolerated and increased time to first seizure for patients with FBTCS. ESL 1200mg significantly improved 50% and 75% responder rates compared to placebo. ESL may be a useful treatment option for FBTCS.