This was a phase III, 2-part multicenter study. Part I was an 26-week parallel-group, randomized, placebo-controlled design consisting of an 8 week baseline period, a 2 week double-blinded titration period, 12 week maintenance period, and a 4 week tapering-off period. After completing the baseline period, patients were randomized in a 1:1:1 ratio to 1 of the 2 ESL daily dose levels (1200 or 800 mg) or placebo.