New trials show acetaminophen better than placebo for OA

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Jul 20, 2004

Sutton-in-Ashfield, UK - Acetaminophen (paracetamol) is more effective than placebo in relieving the pain of large joint osteoarthritis (OA), according to a Leader in the August 2004 issue of the Annals of the Rheumatic Diseases [1]. But NSAIDs and coxibs are superior to acetaminophen, it adds.

Three new papers on acetaminophen and OA accompany this Leader, an unprecedented occurrence. "Never in the 127 years history of acetaminophen's existence have so much trial data on OA been reported,"

The new papers consist of a meta-analysis and 2 large-placebo-controlled studies of the efficacy of acetaminophen in OA.





Meta-analysis: acetaminophen should remain first-line therapy

Although current EULAR and ACR guidelines both support acetaminophen as the first-line oral analgesic for patients with knee OA, "until now there has been a paucity of clinical trial data to confirm the efficacy of paracetamol in large joint OA," Neame et al say in their Leader.

Until now there has been a paucity of clinical trial data to confirm the efficacy of paracetamol in large joint OA.

There have been only 4 placebo-controlled trials of this drug in OA, they note. The first 2 showed the superiority of acetaminophen over placebo, but they were small. A third, slightly larger, study was negative, however, while a fourth crossover study showed that acetaminophen was effective for pain but was no better than placebo for total WOMAC scores.

In the light of these heterogeneous data, Dr Weiya Zhang (University of Nottingham, UK) et al have undertaken a new meta-analysis of evidence available to July 2003 [2].

This included 10 randomized controlled trials and shows that acetaminophen gives pain relief in OA that is better than placebo (effect size 0.21; 95% CI 0.02-0.41).

However, NSAIDs were better than acetaminophen for pain relief, and clinical response rate was higher with NSAIDS than with acetaminophen. Also, the number of patients who preferred NSAIDs was more than twice the number preferring acetaminophen.

Professor Michael Doherty (University of Nottingham, UK)—an author of the Leader and the meta-analysis—told rheumawire that "despite the findings that NSAIDs are more efficacious than paracetamol, the latter should remain first-line therapy for knee OA."

[Paracetamol] should remain first-line therapy for knee OA.

The safety record of acetaminophen at the recommended dosage "is excellent," and "it is very cheap and widely available," he says. Only if acetaminophen proves insufficient should NSAIDs be considered, he believes, because they "can kill you!"

"Most patients with OA are old or elderly and are at increased risk of NSAID-associated peptic ulceration/bleeding/perforation. If they are given NSAIDs they should be considered for prophylaxis (combined proton pump inhibitors [PPIs] or misoprostol) or be given a coxib,"