Analgesics for acute nonspecific low back pain: cautious approach urged

By Rebecca Jenkins

Clinicians should remain cautious about using analgesic medicines to treat acute nonspecific low back pain until higher quality safety and efficacy evidence is published, UK and Australian researchers say.

Analgesics were widely prescribed for nonspecific low back pain lasting less than six weeks, the researchers wrote in The BMJ, but there was no comprehensive evaluation of individual medicines available to inform clinical decision making.

They conducted a systematic review and network analysis of 98 qualifying randomised controlled trials which compared analgesic medicines against each other or placebo for acute nonspecific low back pain but found the evidence around comparative effectiveness and safety was uncertain.

The trials were, published between 1964 and 2021 and included more than 15,000 adult patients and 69 different medicines or combinations including NSAIDs, paracetamol, opioids, anticonvulsant drugs, skeletal muscle relaxants or corticosteroids, the researchers wrote.

They found low to very low confidence evidence suggesting that some analgesic medicines might be superior for reducing pain intensity, including pregabalin and 16 other medicines, compared with placebo.

There was moderate to low confidence for increased adverse events such as nausea, vomiting, drowsiness, dizziness and headache with tramadol, paracetamol plus sustained release tramadol, baclofen and paracetamol plus tramadol compared with placebo.

‘These medicines could increase the risk of adverse events compared with other medicines with moderate to low confidence,’ the researchers wrote.

In a secondary analysis of medicine classes, low or very low confidence evidence showed that seven classes might be associated with small to moderate reductions in pain intensity compared with placebo. However, low confidence showed that two of these classes increased the risk of adverse events compared with placebo.

Coauthor Professor Ric Day, Professor of Clinical Pharmacology at UNSW Medicine’s St Vincent’s Clinical School, Sydney, said the meta-analysis had included data from thousands of patients and allowed indirect comparisons of analgesics to address which were better to treat acute back pain.

‘However, despite decades of clinical trials examining this question, sadly trials comparing analgesics are too few and provide only low or very low confidence in the results so that differentiating between them for effectiveness is difficult,’ he told Medicine Today.

Reliance on advice, reassurance, physical activity and self-management of symptoms remain the core guideline recommendation.

‘Analgesics should remain a second-line option and more caution should accompany those that are associated with more adverse events including opioids and muscle relaxants,’ Professor Day said.

‘More high-quality comparative studies are needed to identify the best of a generally mediocre field.’

BMJ 2023; 380: e072962.