This prospective, randomized, double-blinded study is designed to compare opioid-sparing effect of preemptive and preventive intravenous acetaminophen/ibuprofen fixed-dose combination in patients undergoing robot-assisted radical prostatectomy (RARP). We hypothesize that preemptive administration of intravenous acetaminophen/ibuprofen fixed-dose combination can significantly reduce postoperative opioid consumption and pain severity than preventive administration in patients undergoing RARP.

Adult patients undergoing elective robot-assisted radical prostatectomy are randomly allocated to receive preemptive administration of acetaminophen (1000 mg)/ibuprofen (300 mg) fixed-dose combination (n=77) or preventive administration (n=77). The preemptive administration group will receive intravenous acetaminophen (1000 mg)/ibuprofen (300 mg) for 15 minutes at the end of induction of anesthesia. The preventive administration group will receive same dosage of drug for same duration when surgical site closure starts.

Inclusion Criteria:

• Patients scheduled to undergo elective robot-assisted radical prostatectomy under general anesthesia
• American Society of Anesthesiologists (ASA) physical classification I-II
• Consent to IV-patient controlled analgesia use
• Willingness and ability to sign an informed consent document

Exclusion Criteria:

• Who do not understand or agree with our study
• American Society of Anesthesiologists (ASA) physical classification III-IV
• Chronic usage of opioid analgesics
• Moderate to severe pain with other cause before surgery
• Allergies to anesthetic or analgesic medications used in this study
• Anticipated blood loss larger than 2 liters
• Need for intensive care after surgery
• History of gastric ulcer or gastrointestinal bleeding
• History of liver failure, renal failure or heart failure
• Current alcoholism
• Taking anti-coagulation drugs or history of coagulation disease
• History of bronchial asthma
• Medical or psychological disease that can affect the treatment response
• Taking barbitutate or tricyclic antidepressant

An investigator who is not involved in this study randomly allocates the group and another investigator who dose not evaluate clinical endpoints keeps the result of allocation in a sealed envelope.

On the day of study, the second investigator opens the envelope to check allocation and sends a drug and normal saline in identical looking bottles with label only indicating the order of administration.