The trial consists of a screening/tapering period, treatment period, and follow-up period. The 6-week active treatment period includes an inpatient phase and outpatient phase. Participants who complete the trial may continue treatment under a long-term extension protocol (P05689). Participants who do not continue in the treatment continuation trial (whether they complete the 6-week trial or discontinue prematurely) will have a follow-up visit 7 days after their last dose of trial medication.