BACKGROUND: Intravenous (IV) acetaminophen is used in multimodal analgesia to reduce the amount and duration of opioid use in the postoperative setting.
METHODS: A systematic review of published randomized controlled trials was conducted to define the opioid-sparing effect of IV acetaminophen in different types of surgeries. Eligible studies included prospective, randomized, double-blind trials of IV acetaminophen compared with either a placebo- or active-treatment group in adult (age =18 years) patients undergoing surgery. Trials had to be published in English in a peer-reviewed journal.
RESULTS: A total of 44 treatment cohorts included in 37 studies were included in the systematic analysis. Compared with active- or placebo-control treatments, IV acetaminophen produced a statistically significant opioid-sparing effect in 14 of 44 cohorts (32%). An opioid-sparing effect was more common in placebo-controlled comparisons. Of the 28 placebo treatment comparisons, IV acetaminophen produced an opioid-sparing effect in 13 (46%). IV acetaminophen produced an opioid-sparing effect in only 6% (one out of 16) of the active-control groups. Among the 16 active-control groups, opioid consumption was significantly greater with IV acetaminophen than the active comparator in seven cohorts and not significantly different than the active comparator in eight cohorts.
CONCLUSIONS: The results of this systematic analysis demonstrate that IV acetaminophen is not effective in reducing opioid consumption compared with other adjuvant analgesic agents in the postoperative patient. In patients where other adjuvant analgesic agents are contraindicated, IV acetaminophen may be an option.
A negative study can be as important as a positive one in certain conditions. However, this study has several limitations as highlighted by the authors, and in my opinion, it is possibly not relevant and does not impact our knowledge.
Acetaminophen is useful when other NSAIDs may be contraindicated for several reasons. However, as demonstrated in this systematic review, acetaminophen is not opioid-sparing when compared to an active-control; it is better than nothing (placebo). IV Acetaminophen is expensive compared to oral acetaminophen. So while initially the use of IV Acetaminophen increased, it's use is now restricted to patients who have to remain n.p.o after surgery. It's use has been curtailed for economic reasons and rightly so.
I would have expected these results.
The work loses consistency when mixing different types of surgery.
The topic is of interest, as it is about an important aspect of surgical treatment, regarding opioid sparing analgesia. However, the methodology is not optimal as all that is done is a systematic review, which does not fully answer the study question – is IV acetaminophen a cost-effective and effective treatment pre and post-op. This is sometimes the limitation of a systematic review that does not show a clear and large difference in the different groups, and this is why in most cases systematic reviews, it is not enough and one should strive for a meta-analysis, which could show statistically if and to what kind of an effect is the treatment heading.
This is clinically useful information. Instead of "Evidence for Efficacy.....", I would have preferred something like "Lack of Efficacy....." in the title.