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18-03-2019 | Rheumatology | News | Article

Findings question the use of acetaminophen for pain relief in OA patients

medwireNews: Results of a systematic review suggest that treatment with acetaminophen provides only minimal benefit compared with placebo for patients with osteoarthritis (OA).

“Current clinical guidelines consistently recommend [acetaminophen] as the first-line analgesic medication for hip or knee osteoarthritis, given its low absolute frequency of substantive harm,” say Manuela Ferreira (University of Sydney, New South Wales, Australia) and colleagues.

“However, our results call for reconsideration of these recommendations,” they add.

The analysis included 10 placebo-controlled randomized trials involving a total of 3541 participants with knee or hip OA. Patients were followed up for 1–24 weeks, and the dose of oral acetaminophen ranged from 1.95 to 4.00 g/day.

Ferreira and team report in The Cochrane Library that acetaminophen was associated with minimal improvements in pain scores on a scale of 1–100, with average reductions of 26.23 points for acetaminophen-treated patients compared with 23.00 points for those given placebo.

The absolute difference between the groups, of 3%, was below the minimal clinically important difference (MCID) of 9.00%, note the researchers.

Similarly, physical function scores improved by an average of 14.29 points and 12.00 points in the acetaminophen and placebo groups, respectively, giving a mean between-group difference of 2.92 points, below the MCID of 10%.

The study authors point out that these findings were based on high-quality evidence, and that the impact of acetaminophen on pain and physical function was comparable regardless of the dose used (≤3.0 vs ≥3.9 g/day).

Together, these findings show “that pharmacological management of hip or knee osteoarthritis through simple analgesics only offers small and clinically unimportant effects on pain and physical function,” write the study authors.

They caution, however, that their results “are mostly restricted to immediate- and short-term follow-ups,” with only one trial having a follow-up of more than 12 weeks.

In the safety analysis, Ferreira and colleagues found high-quality evidence to indicate that the incidence of adverse events was similar among acetaminophen- versus placebo-treated patients (328 vs 325 per 1000 people), but there was less certainty regarding the comparative risk for serious adverse events, abnormal liver function tests, and withdrawals due to adverse events due to limited patient numbers.

The team concludes: “Future research should focus on developing and implementing models of care that are focused on evidence-based non-pharmacological approaches for the care of knee and hip osteoarthritis.”

By Claire Barnard

medwireNews is an independent medical news service provided by Springer Healthcare. © 2019 Springer Healthcare part of the Springer Nature group

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