Intravenous administration of acetaminophen (APAP) may be less effective than oral administration of APAP for reducing opioid use after total hip or knee arthroplasty (THA/TKA), according to a study published in Regional Anesthesia and Pain Medicine.

Data from the Premier Healthcare claims database on THA/TKA procedures performed between 2011 and 2016 were examined (n=1,039,647). Researchers determined whether intravenous or oral APAP was used on the day of surgery, as well as on postoperative day 1 and thereafter. Length and cost of hospitalization, opioid-related adverse effects, and opioid use, as reported in oral morphine equivalents, were the outcomes of the analysis.

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A total of 245,454 patients (23.6%) were administered intravenous APAP, and 56.3% of these patients were treated with 1 dose on the day of surgery. In the adjusted analysis, the use of >1 dose of intravenous APAP on postoperative day 1 was associated with a 6.0% reduction in opioid use compared with no use (95% CI, −7.2% to −4.7%). Oral vs intravenous APAP administration on postoperative day 1 was associated with a greater reduction of opioid use (10.7% reduction; 95% CI, −11.4% to −9.9%).

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Patients who received >1 intravenous dose of APAP vs no APAP on the day of surgery experienced reduced odds of respiratory and gastrointestinal adverse effects (odds ratio, 0.80 [95% CI, 0.68-0.94] and odds ratio, 0.77 [95% CI, 0.67-0.89], respectively). Oral vs intravenous APAP administration was associated with more pronounced and consistent opioid reduction patterns that correlated with reduced opioid-related adverse effects.

Limitations of the study include its retrospective nature, as well as the lack of assessment of the effect of APAP on patients’ pain scores.

“[W]henever feasible, APAP can be administered orally, producing similar, if not slightly better effects,” noted the study authors.


Stundner O, Poeran J, Ladenhauf HN, et al. Effectiveness of intravenous acetaminophen for postoperative pain management in hip and knee arthroplasties: a population-based study. Reg Anesth Pain Med. 2019;44(5):565-572.

This article originally appeared on Clinical Pain Advisor