A Study Evaluating the Overall Pain Relief and Safety of Intravenous (IV) CR845 in Patients Undergoing Abdominal Surgery

Patients will be admitted to the surgical center on the day of their abdominal surgery (Day 1, unless admission the night before is required). All patients will be seen by the study staff to confirm eligibility, review study procedures, and conduct all pre-surgical assessments required for randomization. Qualified patients will be randomized into 1 of 3 treatment groups, corresponding to 1 of 2 dose levels of intravenous (IV) CR845 (0.5 or 1 mcg/kg) or matched placebo, respectively. Study drug will be administered every 6 hours during the 24-hour post-operative treatment period following these initial 2 drug administrations: * Pre-Operative dose: Within one hour prior to anesthetic induction for surgery. This dose will be a 2X loading dose. * Baseline post-operative dose: within 30-minutes of being considered stable in the Post-Anesthesia Care Unit (PACU) Subsequent dosing will be administered at 6, 12 and 18 hours. During the Treatment and Observation Period, pain intensity scores will be obtained at specified time points and episodes of nausea or vomiting will be recorded. Upon request, patients may be provided with analgesic or anti-nausea rescue medication (restricted to morphine (if tolerated), and ondansetron, respectively) at any time after the Baseline dose of study drug is administered. Blood sampling and safety assessments will be conducted during this period as well. Patients will remain in the hospital until Day 3 (48-hours after surgery) at which point they will be evaluated for discharge. A follow-up medical evaluation will be scheduled within 7 - 10 days post-surgery.