1. Paracetamol taken regularly or as needed for low-back pain did not affect recovery time compared with placebo.
Evidence Rating Level: 1 (Excellent)
Study Rundown: Although paracetamol is universally recommended as the first-line analgesic for low-back pain, no high-quality evidence has supported this recommendation. The Paracetamol for Low-Back Pain Study (PACE) assessed the efficacy of paracetamol compared to placebo when taken regularly or as needed for low-back pain. Patients with acute low-back pain were randomized to receive either 4 weeks of paracetamol, paracetamol as needed, or placebo, and followed up for three months. Recovery was defined as a pain score of 0 or 1 out of a 0-10 pain scale for 7 consecutive days.
Regardless of whether paracetamol was taken regularly or as needed, there was no significant difference compared to placebo in minimizing recovery time from low-back pain. Strengths of this study included a large sample size of over 500 participants in each group and the study was adequately powered to detect a difference of 3 days in median time to recovery. Limitations of the study include the fact that participants typically took a lower median dose than the maximum recommended dose, which may have affected the efficacy. The authors suggest that the universal recommendation of paracetamol for use in patients with low-back pain be reconsidered, however, further studies should be conducted before completely dismissing paracetamol as a treatment for low-back pain.
This study was funded by the National Health and Medical Research Council of Australia and GlaxoSmithKline Australia.
In-Depth [randomized controlled trial]: Participants were randomly assigned to one of three groups: paracetamol as needed (maximum 4000 mg/day, n=546), paracetamol at a regular dose (3990 mg/day, n=550) or placebo (n=547). The primary outcome was time in days until recovery from pain as defined by a 0 or 1 pain intensity measured on a 0-10 pain scale for 7 days. Secondary outcomes were pain intensity, disability, function, global rating of symptom change, sleep quality, and quality of life.
By 12 weeks, 466 (85%) participants in the regular group, 452 (83%) in the as-needed group, and 461 (84%) in the placebo group reached recovery. The median time to recovery was 17 days (95% Confidence Interval [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 [HR] 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). Time to recovery did not significantly differ between groups (p = 0.55), even when calculating for best-case and worst-case recovery. Participants in all groups reported decreased treatment adherence, decreasing from 3500 mg/day in week 1 to 2800 mg/day in week 2. The median number of tablets taken daily was 4.0 (Interquartile range [IQR] 1.5-5.7, 2660 mg/day) in the regular group, 1.9 (IQR 1.0-4.0, 1000 mg/day) in the as-needed group in week 1 with 1.0 (0.4-2.7, 500 mg/day) daily overall, and 4.0 (IQR 1.5-5.7) daily in the placebo group. Adverse events were similar in all groups, with 99 (18.5%) reported in the regular group, 99 (18.7%) in the as-needed group, and 98 (18.5%) in the placebo group.
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