The purpose of this study is to explore the clinical characteristics oral MNK155 and Norco® 7.5mg/325mg when used for the treatment of moderate to severe post operative pain.

This is a single center, open label, prospective, randomized study on adult post operative subjects who are expected to require oral opioid analgesia for at least 48 hours after surgery. The main study drug of interest in this study is MNK 155. Norco® 7.5mg/325mg is being utilized only as active comparator.

Subjects will be at least 18 years of age and will be scheduled to undergo elective surgery. The following surgical types will be allowed, although the list is not all inclusive:

• Abdominal surgery
• Soft tissue surgery
• Orthopedic surgery
• Spine surgery
• Genitourinary surgery

Inclusion Criteria:

1. Subjects who provide written informed consent prior to enrollment.

2. Male or female and 18 years of age or older.

3. Subjects who are scheduled to undergo elective general surgery including, but not limited to the following surgical types:

   • Abdominal surgery
   • Orthopedic surgery
   • Spine surgery
   • Genitourinary surgery

4. Subjects classified as American Society of Anesthesiologists (ASA class I-III).

5. Female subjects are eligible only if all of the following apply:

   • Not pregnant (subjects of child bearing potential must have a negative beta human chorionic gonadotropin (β-hCG) pregnancy test before surgery);
   • Not lactating;
   • Not planning to become pregnant within the duration of the study;

6. Subjects who are expected to have acute pain requiring oral opioid analgesics for at least 48 hours during the post operative period (either inpatient or outpatient).

7. Subjects who are willing and capable of understanding and cooperating with the requirements of the study.

8. Subjects able to understand and communicate in English.

Exclusion Criteria:

1. Subjects with a medical condition that, in the Investigator's opinion, could adversely impact the subject's participation, safety, or conduct of the study such as but not limited to a history of severe renal or hepatic impairment, severe active hepatic disease, or any other clinically significant medical condition that may preclude safe study participation.