Daily Dose: Safety, Efficacy of Analgesic Medicines for LBP Questioned

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On April 5, 2023, we reported on a study published in The BMJ that evaluated the comparative effectiveness and safety of analgesic medicines for acute non-specific low back pain (LBP).

The study

Researchers conducted a systematic literature review and meta-analysis, beginning with a search of databases including Medline, PubMed, Embase, and Clinicaltrials.gov from inception through February 2022 for RCT comparing analgesic medicines with another analgesics, placebo, or no treatment in patients reporting acute non-specific LBP. Analgesics were defined as nonsteroidal anti-inflammatory drugs (NSAIDs), opioids, corticosteroids, antidepressants, paracetamol, anti-convulsants, and skeletal muscle relaxants. Eligible RCTs involved adults who reported acute non-specific LBP for a period of less than 6 weeks.

The primary outcomes of interest were LBP intensity at the end of treatment (on a 0-100-point scale) and safety (number of participants who reported any adverse event during treatment). Researchers identified secondary outcomes as serious adverse events, low back specific function, and treatment discontinuation. identified 124 relevant trials of which 98 RCTs, published between 1964 and 2021, were included in their final analysis. Final participant count was 15 134; 51% were men and mean age across RCT ranged from 30 to 60 years. Pain duration ranged from 24 hours to 21 days and median pain intensity at baseline for all trials was 65/100. Studies included 169 different analgesics or combinations (42 as monotherapy, 27 as combinations).

Duration of treatment ranged from 1 day to 42 days.

The findings

The researchers noted low or very low confidence in evidence for reduced pain intensity after treatment with muscle relaxant tolperisone, (mean difference −26.1; 95% CI −34.0 to −18.2), pregabalin (−24.7; 95% CI −34.6 to −14.7), aceclofenac plus tizanidine (−26.1; 95% CI −38.5 to −13.6), in addition to 14 other medicines, when compared with placebo. Researchers also noted very low confidence for no difference between the effects of several of these medications. For statistically significant reductions, the research team noted very low confidence reported for large reductions in pain intensity (mean difference >20 points) for 4 medicines (eg, thiocolchicoside, ketoprofen), moderate reductions (10-20 points) for 7 medicines (eg, aceclofenac, etoricoxib, ketorolac) and small reductions (5-10 points) for 3 medicines including ibuprofen and paracetamol.

The researchers noted moderate to very low confidence evidence for increased adverse events, such as nausea, vomiting, drowsiness, dizziness, and headache, with tramadol (risk ratio [RR] 2.6; 95% CI 1.5 to 4.5]), baclofen (2.3; 95% CI 1.5 to 3.4), paracetamol plus tramadol (2.1; 95% CI 1.3 to 3.4), and paracetamol plus sustained release tramadol (2.4; 95% CI 1.5 to 3.8) compared to placebo. Moderate to low confidence evidence also suggested that these medications could increase the risk of adverse events compared to other medications.

Note from authors

"Despite nearly 60 years of research involving more than 15000 patients, high quality evidence to guide clinical decisions on analgesic medicines for acute non-specific low back pain remains limited. Similarly, evidence from the secondary analysis of medicine classes had low confidence. Clinicians and patients are advised to take a cautious approach to the use of analgesic medicines. No further reviews are needed until high quality studies are published."

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