A literature review of randomized clinical trials of intravenous acetaminophen (paracetamol) for acute postoperative pain.

INTRODUCTION: This study's objective was to systematically review the literature to assess analgesic outcomes of intravenous (IV) acetaminophen for acute postoperative pain in adults.
METHODS: We searched Medline and the Cochrane library (January 1, 2000 to January 17, 2010, date of last search) for prospective, randomized, controlled trials (RCTs) of IV acetaminophen vs. either an active comparator or placebo.
RESULTS: Sixteen articles from 9 countries published between 2005 and 2010 met inclusion criteria and had a total of 1,464 patients. Median sample size=54 patients (range 25 to 165) and median follow-up=1 day (range 1 hour to 7 days). Four of the 16 articles had 3 arms in the study. One article had 4 arms. As a result, 22 study comparisons were analyzed: IV acetaminophen to an active comparator (n=8 studies) and IV acetaminophen to placebo (n=14 studies). The RCTs were of high methodological quality with Jadad median score=5. In 7 of 8 active comparator studies (IV parecoxib [n=3 studies], IV metamizol [n=4], oral ibuprofen [n=1]), IV acetaminophen had similar analgesic outcomes as the active comparator. Twelve of the 14 placebo studies found that IV acetaminophen patients had improved analgesia. Ten of those 14 studies reported less opioid consumption, a lower percentage of patients rescuing, or a longer time to first rescue with IV acetaminophen. Formal meta-analysis pooling was not performed because the studies had different primary end points, and the IV acetaminophen dosing regimens varied in dose, and duration and timing.
CONCLUSION: In aggregate, these data indicate that IV acetaminophen is an effective analgesic across a variety of surgical procedures.