This is a randomized, double-blinded, placebo- controlled, and cross-over clinical trial. 147 subjects will be enrolled at two clinical sites, with projected 9-10% dropout and anticipated 134 completed subjects. To maintain blinding of the investigators, the study randomization table will be kept in Pharmacy Service. The sponsor will ship the study drug directly to the Pharmacy Service. The pharmacy service will also be responsible for dispersing the study drug.