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.

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.

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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.