All patients to be considered for recruitment to this study will be undergoing delivery at John Sealy Hospital at the University of Texas Medical Branch in Galveston, Texas. Patients with an elevated BMI >or =30 kg/m2 who undergo cesarean section after laboring will be considered for randomization either prior to delivery or in the first 7 hours after delivery, to accommodate the need for the first dose of study medication or placebo 8 hours after surgery. Only patients who agree to inclusion after informed consent will be randomized per protocol.