Paracetamol ineffective for the pain relief of lower back pain and hip/knee osteoarthritis

1. Paracetamol (acetaminophen) was found to be ineffective at significantly reducing pain symptoms in patients with lower back and hip/knee osteoarthritis pain.

2. While long-term benefits could not be evaluated in this study, high-quality evidence suggests prescription of paracetamol for short-term pain relief is not supported.

Evidence Rating Level: 1 (Excellent)

Study Rundown: Lower back pain and osteoarthritis of the knee and hip are amongst the leading causes of disability in the United States. Paracetamol is commonly recommended as a first line drug by both prescribers and guidelines. Despite its common use, there has been controversy about the efficacy of paracetamol in pain resulting from these conditions. This systematic review and meta-analysis compiled and offered recommendations regarding paracetamol efficacy for pain amelioration in osteoarthritis of the back and knee and lower back pain. Primary and secondary study characteristics were extracted from randomized control trials comparing paracetamol versus placebo. Primary endpoints included pain intensity, disability status, and quality of life; secondary endpoints included adverse effects, medication compliance, and the use of a rescue medication. Oral paracetamol was used in the trials that were included in this study with the exception of one trial where IV paracetamol was used to treat chronic back pain. Paracetamol showed no effect on spinal pain and small benefit on osteoarthritic pain as compared to placebo. Although the occurrence of adverse events was similar between groups, patients using paracetamol were four times as likely to have elevated liver function tests. Participants that were taking paracetamol were equally as likely to use rescue medications such as ibuprofen or naproxen as patients taking a placebo.

The studies included in this systematic review and meta-analysis were generally considered to be of “high quality” evidence as per GRADE system for judging evidence quality. However, the individual meta-analyses for spinal and hip/knee osteoarthritis pain pooled data from a small number of studies and did not record long-term follow-up data. Nevertheless, this study represents the most recent and most thorough evaluation of paracetamol effectiveness for lower back pain and hip and knee osteoarthritis. It provides evidence against paracetemol prescription to significantly lower pain in either situation and should help direct clinical guidelines moving forward.

Click to read the study in the BMJ

Click to read an accompanying editorial in the BMJ

Relevant Reading: Paracetamol: are therapeutic doses entirely safe?

In-Depth [systematic review and meta-analysis]: This study assessed the effectiveness of paracetamol for the treatment of spinal pain and osteoarthritis. Inclusion criteria consisted of study of pain intensity, disability status, and/or quality of life. Secondary outcomes included safety, patient adherence, and use of rescue medications. Studies were excluded if they studied effectiveness during the post-op period or patients with pre-existing spine pathology. A total of 13 randomized control trials were identified for review of which 10 trials studied the max dose of 3900-4000mg/day while 3 trials studied a 3000mg/day dose. Ineffectiveness of paracetamol was defined as crossing the 95% confidence interval showing no difference between paracetamol and the placebo group. Effectiveness for pain reduction was based on differences in pain scores on a 1-100 scale. Paracetamol was ineffective in the treatment of lower back pain as compared to placebo (CI95 -1.3 to 4.1). Paracetamol had a small benefit in the treatment of hip or knee osteoarthritis as compared to placebo with a -3.3 (CI95 -5.8 to -0.8) difference in the pain score. Occurrence of adverse events was no different between participants who took paracetamol compared to placebo. Patients taking paracetamol were 3.8 (CI95 1.9 to 7.4) times more likely to have elevated liver function tests. Rescue medications were utilized equally in patients taking paracetamol as compared to placebo.

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