Evidence for Safety, Efficacy of Analgesics for Acute Low Back Pain Is Limited

The evidence surrounding the effects of analgesics for acute low back pain remain uncertain, according to study findings in published in the BMJ.

While analgesic medications are recommended as second-line therapy in the treatment of acute nonspecific lower back pain, there is no specific guidance on which one is superior. Researchers conducted a systematic review and meta-analysis to compare the safety and efficacy of using analgesics for acute low back pain.

The studies were randomized control trials that compared analgesic medications to each other, with a placebo, or with no treatment. Analgesic medications considered for inclusion were nonsteroidal anti-inflammatory drugs (NSAIDs), paracetamol, opioids, anticonvulsants, antidepressants, skeletal muscle relaxants, and corticosteroids.

The researchers searched 5 databases and 3 clinical registers (Medline, PubMed, Embase, CINAHL, the Cochrane Central Register of Controlled Trials, ClinicalTrials.gov, EU Clinical Trials Register, and the World Health Organization’s International Clinical Trial Registry Platform) and identified 98 trials for analysis.

The studies were conducted in adults with acute nonspecific lower back pain. Medications were administered systemically for at least 24 hours and nonsystemic analgesics were excluded from the analysis.

The primary outcomes were safety and lower back pain intensity rated on a scale of 0 to 100 at the end of treatment. Secondary outcomes were serious adverse events, lower back function, and discontinuation of treatment. 

Out of 741 medication comparisons, 87% comparisons showed very low confidence and 13% showed low confidence in reducing pain intensity. Medications showing low or very low confidence for reducing pain intensity were 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 when compared with placebo.

Of the 98 trials in the study, 68 trials analyzed medication adverse events. There is moderate to low confidence for evidence of increased adverse events for patients taking tramadol (risk ratio [RR], 2.6; 95% CI, 1.5-4.5), paracetamol plus sustained-release tramadol (RR, 2.4; 95% CI, 1.5-3.8), baclofen (RR, 2.3; 95% CI, 1.5-3.4), and paracetamol plus tramadol (RR, 2.1; 95% CI, 1.3-3.4) compared with placebo.

Safety was assessed in 46 trials and direct evidence was revealed for 171 analgesic comparisons. Of these comparisons, 4% were very low confidence, 65% were low confidence, 29% were moderate confidence, and 3% were high confidence.

Of note, some adverse events were associated with the use of nonselective NSAIDs plus strong opioids plus paracetamol (RR, 1.9; 95% CI, 1.1-3.2; high confidence), weak opioids plus paracetamol (RR, 1.9; 95% CI, 1.3-2.7; moderate confidence), and nonselective NSAIDs plus nonbenzodiazepine antispasmodic (RR, 1.5; 95% CI, 1.1-2.1, moderate confidence).

“The structure of this information is not yet optimal to inform clinical decision making and the potential for network meta-analysis to contribute improved estimates of effects was under-realised,” the researchers noted. “Most estimates were derived solely from indirect evidence, a key contributor to the low or very low confidence.”

Study limitations included the risk of bias across most studies, missing data, and the inability to determine the impact of potential effect modifiers.

The researchers concluded, “The comparative effectiveness and safety of analgesic medicines for acute non-specific low back pain are uncertain.”

Disclosure: Some study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures.