 Patients will participate in the study for approximately 44 to 56 days, including a 14- to 21-day Screening Period, 4 Treatment Periods each followed by washout periods, and a final Follow-up Visit. Patients will receive their randomly assigned study medication and spend 2 nights in a sleep laboratory, subsequently returning home for a 4- to 7-day washout period between each treatment period. The fourth and final treatment period will include a third night at the site during which all patients will continue to receive the same study medication as on the first 2 nights of this treatment period. Blood will be drawn from all patients for pharmacokinetic analyses at specific time intervals. Patients will undergo final safety assessments 2 to 5 days after the last dose of study medication. 