The purpose of this study is to assess the effectiveness, safety and pharmacokinetics of Oral Nalbuphine in the treatment of postoperative pain following hemorrhoidectomy.

• Primary Efficacy Endpoint: Pain assessment calculated as the area under the curve of VAS pain intensity scores through 48 hours.

• Secondary Efficacy Endpoints:

1. Consumption of diclofenac (Day 1-2) via Intramuscular Injection (IM injection).
2. Time from the end of operation to the first IM injection diclofenac dose
3. Brief Pain Inventory (BPI).
4. Patient satisfaction.

Inclusion Criteria:

1. Male or female >= 20 years of age at Screening
2. Scheduled to electively undergo 2 or 3-column excisional hemorrhoidectomy
3. American Society of Anesthesiology Physical Class 1 - 3
4. Clinical lab values twice the upper limit of normal (values of potential clinical concern are detailed in Appendix) or, if abnormal, deemed not clinically significant per the Investigator.
5. Ability and willingness to provide informed consent, adhere to the study visit schedule and complete all study assessments and language specific questionnaires.

Exclusion Criteria:

1. Body weight less than 40 kg.
2. Concurrent fissurectomy.
3. Subject is pregnant or breastfeeding. Women of childbearing potential must have a negative urine pregnancy test at Baseline.
4. Women of childbearing potential disagree to use an acceptable method of contraception (e.g., hormonal contraceptives, Intrauterine Device (IUD), barrier device or abstinence) throughout the study.
5. History of hypersensitivity or allergy to amide-type local anesthetics, opioid, or any ingredient of the medications administered in this study.
6. Subject has a resting respiratory rate less than 8 per minute and blood oxygen saturation less than 90 mmHg.
7. Use of any NSAIDs, selective Cyclooxygenase-2 Inhibitors, opioid, acetaminophen, selective serotonin reuptake inhibitors (SSRI), tricyclic antidepressants (TCA), gabapentin, or pregabalin within three days of surgery.
8. Chronic use of opioid medications for more than 14 days in the last 3 months, or non-opioid pain medications more than 5 times per week.
9. Use of any long-acting opioid medication within 3 days of surgery or any opioid medication within 24 hours of surgery.
10. Current painful physical condition or concurrent surgery requires analgesic treatment in the postoperative period.
11. Contraindication to epinephrine or any of the pain-control agents planned for postoperative use.
12. Administration of an investigational drug within the longer of 30 days or 5 elimination half-lives of such investigational drug prior to study drug administration.
13. Any psychiatric disorder, psychological, medical, or laboratory condition that may interfere with study assessments or compliance.
14. Significant medical conditions or laboratory results that may indicate an increased vulnerability to study drugs and procedures, and thus expose the subject to an unreasonable risk as a result of participating in this clinical trial.
15. Any clinically significant event or condition uncovered during surgery.
16. History of abuse illicit drugs, prescription medicines or alcohol within the past 2 years.
17. Known history of anti-HIV antibody positive .
18. Failure to pass drug and alcohol screen.