Efficacy of Paracetamol for Acute Low-Back Pain: A Double-Blind, Randomised Controlled Trial

Lancet. 2014 Nov 1;384(9954):1586-96. doi: 10.1016/S0140-6736(14)60805-9. Epub 2014 Jul 23.

Abstract

Background: Regular paracetamol is the recommended first-line analgesic for acute low-back pain; however, no high-quality evidence supports this recommendation. We aimed to assess the efficacy of paracetamol taken regularly or as-needed to improve time to recovery from pain, compared with placebo, in patients with low-back pain.

Methods: We did a multicentre, double-dummy, randomised, placebo controlled trial across 235 primary care centres in Sydney, Australia, from Nov 11, 2009, to March 5, 2013. We randomly allocated patients with acute low-back pain in a 1:1:1 ratio to receive up to 4 weeks of regular doses of paracetamol (three times per day; equivalent to 3990 mg paracetamol per day), as-needed doses of paracetamol (taken when needed for pain relief; maximum 4000 mg paracetamol per day), or placebo. Randomisation was done according to a centralised randomisation schedule prepared by a researcher who was not involved in patient recruitment or data collection. Patients and staff at all sites were masked to treatment allocation. All participants received best-evidence advice and were followed up for 3 months. The primary outcome was time until recovery from low-back pain, with recovery defined as a pain score of 0 or 1 (on a 0-10 pain scale) sustained for 7 consecutive days. All data were analysed by intention to treat. This study is registered with the Australian and New Zealand Clinical Trial Registry, number ACTN 12609000966291.

Findings: 550 participants were assigned to the regular group (550 analysed), 549 were assigned to the as-needed group (546 analysed), and 553 were assigned to the placebo group (547 analysed). Median time to recovery was 17 days (95% CI 14-19) in the regular group, 17 days (15-20) in the as-needed group, and 16 days (14-20) in the placebo group (regular vs placebo hazard ratio 0·99, 95% CI 0·87-1·14; as-needed vs placebo 1·05, 0·92-1·19; regular vs as-needed 1·05, 0·92-1·20). We recorded no difference between treatment groups for time to recovery (adjusted p=0·79). Adherence to regular tablets (median tablets consumed per participant per day of maximum 6; 4·0 [IQR 1·6-5·7] in the regular group, 3·9 [1·5-5·6] in the as-needed group, and 4·0 [1·5-5·7] in the placebo group), and number of participants reporting adverse events (99 [18·5%] in the regular group, 99 [18·7%] in the as-needed group, and 98 [18·5%] in the placebo group) were similar between groups.

Interpretation: Our findings suggest that regular or as-needed dosing with paracetamol does not affect recovery time compared with placebo in low-back pain, and question the universal endorsement of paracetamol in this patient group.

Funding: National Health and Medical Research Council of Australia and GlaxoSmithKline Australia.

Publication types

  • Multicenter Study
  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acetaminophen / administration & dosage
  • Acetaminophen / therapeutic use*
  • Acute Pain / drug therapy*
  • Adult
  • Analgesics, Non-Narcotic / administration & dosage
  • Analgesics, Non-Narcotic / therapeutic use*
  • Double-Blind Method
  • Drug Administration Schedule
  • Female
  • Humans
  • Kaplan-Meier Estimate
  • Low Back Pain / drug therapy*
  • Male
  • Medication Adherence / statistics & numerical data
  • Middle Aged
  • Pain Measurement / methods
  • Socioeconomic Factors
  • Treatment Outcome

Substances

  • Analgesics, Non-Narcotic
  • Acetaminophen

Associated data

  • ANZCTR/ACTN12609000966291