Cumulative exit rate at day 112, based on the duration between start date of previous AED tapering to the earliest date exit criterion was met; calculated using Kaplan Meier Methods. Subjects prematurely discontinued for reasons unrelated to exit criteria were censored as of last dose of study drug. Subjects who completed without meeting exit criteria were censored at Day 112. Exit criteria include increase in seizure frequency, severity, duration, status epilepticus, or new generalized seizure. Upper 95% 2-sided confidence limit for exit rate is compared to the historical control rate: 0.678.

Of the 171 (Keppra 2000 mg) subjects randomized, 158 subjects entered the Previous Antiepileptic Drug Tapering Phase and were included in the Efficacy Population. Primary Efficacy analysis was conducted for the Keppra XR 2000 mg/day group only.

The cumulative exit event rate at Day 112 was calculated using Kaplan Meier methods. The exit event rate estimate was based on the duration between the start date of previous AED tapering to the earliest date an exit event occured. Subjects who prematurely discontinued for reasons unrelated to exit criteria, adverse event, or lack of efficacy were censored as of the last dose of study medication. Subjects who completed the study without having an exit event were censored as of Day 112.

Of the 171 (Keppra 2000 mg) subjects randomized, 158 subjects entered the Previous Antiepileptic Drug Tapering Phase and were included in the Efficacy Population. Evaluated for Keppra XR 2000 mg/day only.

The cumulative exit event rate at Day 112 was calculated using Kaplan Meier methods. The exit event rate estimate was based on the duration between the start date of previous AED tapering to the earliest date an exit event occured. Subjects who completed the study without having an exit event were censored as of Day 112.

Of the 171 (Keppra 2000 mg) subjects randomized, 158 subjects entered the Previous Antiepileptic Drug Tapering Phase and were included in the Efficacy Population. Evaluated for Keppra XR 2000 mg/day only.

Keppra XR 1000 mg arm was not intended for inferential analysis (planned 3 to 1 randomization, Keppra XR 2000 mg: 1000 mg). The Exit Rate was based on the duration between the start date of previous AED tapering to the earliest date an exit crterion was met. Subjects who prematurely discontinued for reasons unrelated to exit criteria were censored as of the last dose of study medication. Subjects who completed the study without meeting an exit criterion were censored as of Day 112.

Of the 57 (Keppra 1000 mg) subjects randomized, 54 subjects entered the Previous Antiepileptic Drug Tapering Phase and were included in the Efficacy Population.