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Regular or as-needed paracetamol does not hasten recovery from low back pain compared with placebo, according to a randomised trial that involved 235 primary care centres – including 50 pharmacists – in Australia.

During the study, 550 patients with acute lower back pain took paracetamol regularly three times per day (3,990mg per day) for up to four weeks. Another 546 took paracetamol when needed (maximum 4,000mg per day) and 547 received placebo, again for four weeks.

At baseline, patients (mean age 45 years; 53 per cent men) reported a mean pain intensity of 6.3 on a 0-10 scale. On average, pain began 9.9 days before enrolment. The treatment’s credibility and participants’ expectations – factors that can influence the placebo response – were high and similar across groups.

After 12 weeks, 85 per cent of those taking regular paracetamol, 83 per cent taking the analgesic as-needed and 84 per cent in the placebo group showed a sustained recovery (pain score of zero or one for seven consecutive days). Median times to recovery were 17 days among those taking regular and as-needed paracetamol, and 16 days in the placebo group.

Adherence and the number of patients reporting adverse events (18.5 to 18.7 per cent) were similar between groups. Paracetamol did not improve pain, disability, function, change in global symptoms, sleep quality or quality of life compared to placebo.

“Simple analgesics such as paracetamol might not be of primary importance in the management of acute lower back pain,” said lead author Christopher Williams from the George Institute for Global Health at the University of Sydney. “The results suggest we need to reconsider the universal recommendation to provide paracetamol as a first-line treatment for low back pain, although understanding why paracetamol works for other pain states but not low back pain would help direct future treatments.

“In view of the quick timeframe in which participants in our trial improved compared with other cohorts, it would be interesting to see whether advice and reassurance (as provided in our trial) might be more effective than pharmacological strategies for acute episodes of lower back pain.”