Time of Intravenous Acetaminophen Administration

The purpose of the study is to examine the effects of timing of administration of intravenous (IV) acetaminophen and how timing relates to analgesic efficacy as measured by postoperative pain scores. A maximum of 138 patients meeting inclusion criteria who present for a scheduled total hip replacement under general anesthesia will be randomized into one of two arms: 1) the pre-closure group will receive the first dose administered upon onset of skin closure, 2) the preemptive group will receive the first dose administered within 60 minutes prior to incision. Both groups will receive subsequent doses every 6 hours x 24 hours.