Randomized trial of oral versus intravenous acetaminophen for postoperative pain control.

PURPOSE: Results of a study comparing pain control outcomes with preoperative oral versus intraoperative i.v. acetaminophen use in adults undergoing total hip or knee arthroplasty are reported. METHODS: A single-center, randomized, placebo-controlled, equivalence trial was conducted. Patients were assigned (1:1) to receive 2 500-mg capsules of acetaminophen before surgery, with an i.v. placebo infusion during surgery (the oral group), or 2 oral placebo capsules followed by an i.v. infusion of acetaminophen 1,000 mg/100 mL (the i.v. group). Patients were followed after postanesthesia care unit (PACU) admission up to 24 hours postoperatively. RESULTS: Among 486 patients included in a modified intention-to-treat analysis (mean ± S.D. age, 66.3 ± 9.4 years), there were no significant differences in preoperative and intraoperative use of pain medication between the oral and i.v. groups. Postoperative opioid use in morphine milligram equivalents (MMEs) was equivalent in the oral and i.v. groups (i.e., the mean difference in median MME values was within the prespecified equivalence margin), with no significant between-group differences in mean pain scores over 24 hours. CONCLUSION: In patients undergoing hip or knee arthroplasty, oral acetaminophen given preoperatively was equivalent to i.v. acetaminophen administered in the operating suite in controlling pain in the immediate postoperative period. I.V. acetaminophen was not superior to oral acetaminophen in reducing postoperative nausea and vomiting, time to ambulation, time to first dose of as-needed pain medication, length of PACU stay, or total length of hospital stay.