‘Considerable uncertainty’ surrounds efficacy, safety of analgesics for low back pain

High-certainty evidence on the effectiveness and safety of commonly used analgesics for short bouts of low back pain remains lacking, a systematic review and meta-analysis found.

Researchers analyzed 98 randomized controlled trials published between 1964 and 2021 that compared an analgesic with another analgesic, placebo, or no treatment in patients reporting acute nonspecific low back pain. The trials involved 15,134 adults using 69 different medicines or combinations, including NSAIDs, acetaminophen, opioids, anticonvulsant drugs, muscle relaxants, and corticosteroids. The main measures of interest were low back pain intensity at the end of treatment, on a scale of 0 to 100, and safety, defined as the number of participants who reported any adverse event during treatment. Secondary outcomes were low back- specific function, serious adverse events, and treatment discontinuation. Average pain intensity among participants at the start of each trial was 65 out of 100. Results were published March 22 by The BMJ.

The authors noted low or very low confidence in the evidence for reduced pain intensity after treatment with tolperisone (mean difference, −26.1; 95% CI, −34.0 to −18.2), aceclofenac plus tizanidine (mean difference, −26.1; 95% CI, −38.5 to −13.6), pregabalin (mean difference,−24.7; 95% CI, −34.6 to −14.7), and 14 other medicines compared with placebo. There was moderate to very low confidence in the evidence for increased adverse events with tramadol (risk ratio [RR], 2.6; 95% CI, 1.5 to 4.5), acetaminophen plus sustained-release tramadol (RR, 2.4; 95% CI, 1.5 to 3.8), baclofen (RR, 2.3; 95% CI, 1.5 to 3.4), and acetaminophen plus tramadol (RR, 2.1; 95% CI, 1.3 to 3.4) compared with placebo.

There was very low confidence in the evidence of large reductions in pain intensity (around 20 points) for four treatments, including thiocolchicoside and ketoprofen; moderate reductions (10 to 20 points) for seven treatments, including aceclofenac, etoricoxib, and ketorolac; and small reductions (5 to 10 points) for three treatments, including ibuprofen and acetaminophen.

The evidence for increased adverse events, such as nausea, vomiting, drowsiness, dizziness, and headache, with tramadol, acetaminophen plus sustained-release tramadol, baclofen, and acetaminophen plus tramadol versus placebo was of moderate to low confidence. The study also found evidence of similar moderate to low confidence for other secondary outcomes, as well as a secondary analysis of medication classes.

The authors noted that they included trials of medications licensed in the U.S., Europe, Australia, and the United Kingdom and that some may not be available everywhere. They concluded that high-quality evidence to guide clinical decisions about use of analgesic medicines for acute nonspecific low back pain remains limited and that there is “considerable uncertainty” about their safety and effects on pain intensity. “Clinical practice guidelines recommend non-pharmacological treatments in first line and second line care for acute non-specific low back pain. Given the favourable natural history for most patients, we believe that clinicians and patients should take a cautious approach to the use of analgesic medicines,” they wrote.