Background: Patients with low back pain (LBP) are often treated with non-steroidal anti-inflammatory drugs (NSAID) and skeletal muscle relaxants (SMR). We compared functional outcomes and pain among acute LBP patients randomized to a one week course of ibuprofen + placebo versus ibuprofen + one of three SMRs: baclofen, metaxalone, or tizanidine.
Methods: This was a randomized, double-blind, parallel group, 4-arm study conducted in two urban EDs. Patients with non-radicular LBP for no longer than two weeks were eligible for participation if they had a score greater than 5 on the Roland-Morris Disability Questionnaire (RMDQ), a 24-item inventory of functional impairment due to LBP. All participants received 21 tablets of ibuprofen 600mg, to be taken TID, as needed. Additionally, they were randomized to baclofen 10mg, metaxalone 400mg, tizanidine 2mg, or placebo. Participants were instructed to take one or two of these latter capsules, TID, as needed for LBP. All participants received a 10 minute educational session.The primary outcome was improvement on the RMDQ between ED discharge and 1week later. Secondary outcomes included pain intensity one week after ED discharge (severe, moderate, mild, or none).
Results: 320 patients were randomized. One week later, the mean RMDQ score of patients randomized to placebo improved by 11.1(95%CI:9.0,13.3), baclofen improved by 10.6 (95%CI:8.6,12.7), metaxalone improved by 10.1 (95%CI:8.0,12.3) and tizanidine improved by 11.2 (95%CI:9.2, 3.2). At one week follow-up, 30% (95%CI: 21, 41%) of placebo patients reported moderate/severe LBP versus 33% (95%CI: 24, 44%) of baclofen, 37% (95%CI: 27, 48%) of metaxalone and 33% (95%CI: 23, 44%) of tizanidine patients.
Conclusion. Adding baclofen, metaxalone, or tizanidine to ibuprofen does not appear to improve functioning or pain any more than placebo + ibuprofen one week after an ED visit for acute LBP.