 At the beginning of the Dose-Optimization Phase 3rd week of study drug subjects will take 600 mgday 200 mg TID for one week. Thereafter during the Dose-Optimization Phase, subjects will continue to increase their daily dose by 150 mg per week until they have achieved their optimal tolerated dose. During this phase, the investigator may choose to have the subject stay on hisher designated dose for another week before attempting a dose increase until reaching a dose of 1200 mgday. In addition, in the context of tolerability issues, the subject may be reduced to the preceding dose level for one week before attempting to increase the dose again at the next scheduled time point until the subject reaches optimal dose. Subjects unable to tolerate a minimum of 600 mgday will be discontinued from the study. 