Low back pain (LBP) accounts for 2.6 million visits to emergency rooms (EDs) in the United States annually. Skeletal muscle relaxants are frequently used to treat these individuals (SMRs). For a study, researchers sought to determine if the efficacy of SMRs was related to age, gender, or baseline LBP severity. It was a planned study of data from four randomized clinical trials of individuals with acute nonradicular LBP. Patients were enrolled during an emergency department visit and followed up one week later. The major goal was to see if the Roland-Morris Disability Questionnaire (RMDQ) improved between ED discharge and the 1-week follow-up. The change in RMDQ was examined across eight groups: placebo, baclofen, metaxalone, tizanidine, diazepam, orphenadrine, methocarbamol, and cyclobenzaprine. A nonsteroidal anti-inflammatory medicine was also given to each patient. They used analysis of variance to assess if there were statistically significant differences across drugs and linear regression to determine the relationship between age, gender, baseline severity, and the primary result.

The mean improvement in RMDQ was 10.5 (95% CI 9.5–11.5) for placebo, 10.6 (95% CI 8.6–12.7) for baclofen, 10.3 (95% CI 8.1–12.4) for metaxalone, 11.5 (95% CI 9.5–13.4) with tizanidine, 11.1 (95% CI 9–13.2) for diazepam, orphenadrine 9.5 (95% CI 7.4–11.5). The differences between groups were not statistically significant. The results were consistent independent of age, gender, or baseline severity. Greater clinical improvement was linked with higher baseline RMDQ (B coefficient 5.7, P<0.01). Cyclobenzaprine was associated with greater adverse drug effects than placebo (P<0.01). SMRs did not enhance outcomes more than placebo in individuals with acute LBP treated in the ED with a nonsteroidal anti-inflammatory medication. The findings were unaffected by age, gender, or baseline disability.