The investigators hypothesis is that use of IV acetaminophen will significantly decrease use of post-operative opioid consumption and enhances recovery after colorectal surgery.

All patients undergoing laparoscopic and open colorectal surgery are randomized to receive either IV acetaminophen or placebo. All patients received an opioid patient controlled anesthesia (PCA). IV acetaminophen (1 gram) or placebo is given 30 minutes prior to operation and every 6 hours thereafter for up to 5 days post-operatively or discharge.

The investigators primary endpoint is to evaluate opioid consumption during the patient's hospital stay. The investigators secondary endpoints are to evaluate return of gastrointestinal function (ROGIF), time to diet ordered (TTDO), length of hospital stay (LOHS) and occurrence of ileus. Pain is measured with the pain visual analog scale score (PVASS) at 3, 8, 24 and 48 hours.

Inclusion Criteria:

• Patient undergoing colorectal operation (Hartmann's procedure, sigmoidectomy, left hemicolectomy, right hemicolectomy, transverse colectomy, ileocecectomy, colo-colonic anastomosis, colorectal anastomosis, ileo-colonic anastomosis, low anterior resection, or abdominoperineal resection)
• Age range from 18 to 90 years old
• Patient providing signed, written informed consent before participation in the study

Exclusion Criteria:

• Patient younger than 18 years old or older than 90 years old
• Patient or family is unable to give consent
• Patient who use opioids or tramadol daily for >7 days before study medication administration(patient who, in the investigator's opinion, had or was developing opioid tolerance)
• Patient who had a chronic pain condition or any significant medical disease, laboratory abnormality, or condition that, in the investigator's judgment, could have compromised the subject's welfare, ability to communicate with the study staff, complete study activities, or otherwise restricted study participation
• Patient who had hypersensitivity to opioids, acetaminophen, or the inactive ingredients of the study medication
• Patient who had known or suspected history of alcohol or drug abuse or dependence within the previous 1 year
• Patient who had impaired liver function
• Patient who had fever within first 48 hours post-operatively and required acetaminophen for fever reduction