 This is a randomized, placebo- and positive-controlled moxifloxacin, 3-period, 3-way crossover thorough QT study, which includes a Screening Period, Treatment Periods 1 through 3, and a Follow-up Visit. Subjects will be confined to the investigational site for 4 nights3 days during Period 1 and for 3 nights2 days during Periods 2 and 3. There will be a minimum of a 14 day washout between treatments. 