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Diclofenac More Effective Than Acetaminophen For Knee Osteoarthritis Pain

Diclofenac sodium has been shown to be more effective than acetaminophen in symptomatic treatment for osteoarthritis (OA) of the knee.

This finding is the result of a randomised, double-blind, placebo-controlled trial of 82 patients with symptomatic OA of the medial knee. The study was led by Dr. John Case from Rush Medical College, Rush University, Chicago, Illinois, United States.

Current treatment recommendations call for acetaminophen over nonsteroidal anti-inflammatory drugs (NSAIDs) in the initial treatment of symptomatic OA of the hip or knee because acetaminophen is believed to have less toxicity and equal analgesic efficacy, the clinicians point out.

Dr. Case's literature review, however, found little evidence for a therapeutic effect of acetaminophen relative to placebo in patients with OA of the knee. Most published studies are compound comparative, such as with nonsteroidal anti-inflammatory drugs only.

The present cohort was closely matched by age, sex, body mass index, past use of osteoarthritis medication, pain, and the radiographic features of their illness at baseline.

Twenty-five patients were randomised to receive diclofenac sodium 75 mg twice daily, another 29 patients to receive acetaminophen 1000 mg four times a day. Twenty eight patients received a placebo.

At weeks 2 and 12, using the Western Ontario and McMaster Universities Osteoarthritis Index, there were clinically and statistically significant (P<.001) improvements among the patients treated with diclofenac. In contrast, no significant improvements were seen in the acetaminophen-treated group.

When the patients were stratified according to baseline pain scores, previous osteoarthritis medication use, and radiographic grade, there was no clear pattern of preferential response to diclofenac. In addition, the findings did not reveal a subset of patients who responded to acetaminophen.

Dr. Case and colleagues conclude: "The advocacy of acetaminophen use in subjects with OA of the knee should be reconsidered pending further placebo-controlled studies."
Arch Intern Med Jan 2003;163:2:169-178. "Lack of Efficacy of Acetaminophen in Treating Symptomatic Knee Osteoarthritis : A Randomized, Double-blind, Placebo-Controlled Comparison Trial With Diclofenac Sodium"

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