A Randomized, Placebo-Controlled Trial of Ibuprofen Plus Metaxalone, Tizanidine, or Baclofen for Acute Low Back Pain

Study objective: Patients with low back pain are often treated with nonsteroidal anti-inflammatory drugs and skeletal muscle relaxants. We compare functional outcomes and pain among patients with acute low back pain who were randomized to a 1-week course of ibuprofen plus placebo versus ibuprofen plus 1 of 3 skeletal muscle relaxants: baclofen, metaxalone, and tizanidine. Methods: This was a randomized, double-blind, parallel-group, 4-arm study conducted in 2 urban emergency departments (EDs). Patients with nonradicular low back pain for less than or equal to 2 weeks were eligible if they had a score greater than 5 on the Roland-Morris Disability Questionnaire, a 24-item inventory of functional impairment caused by low back pain. All participants received 21 tablets of ibuprofen 600 mg, to be taken 3 times a day as needed. Additionally, they were randomized to baclofen 10 mg, metaxalone 400 mg, tizanidine 2 mg, or placebo. Participants were instructed to take 1 or 2 of these capsules 3 times a day as needed. All participants received a 10-minute educational session. The primary outcome was improvement on the Roland-Morris Disability Questionnaire between ED discharge and 1week later. Secondary outcomes included pain intensity 1 week after ED discharge (severe, moderate, mild, or none). Results: Three hundred twenty patients were randomized. One week later, the mean Roland-Morris Disability Questionnaire score of patients randomized to placebo improved by 11.1 points (95% confidence interval [CI] 9.0 to 13.3), baclofen by 10.6 points (95% CI 8.6 to 12.7), metaxalone by 10.1 points (95% CI 8.0 to 12.3), and tizanidine by 11.2 points (95% CI 9.2 to 13.2). At 1-week follow-up, 30% of placebo patients (95% CI 21% to 41%) reported moderate to severe low back pain versus 33% of baclofen patients (95% CI 24% to 44%), 37% of metaxalone patients (95% CI 27% to 48%), and 33% of tizanidine patients (95% CI 23% to 44%). Conclusion: Adding baclofen, metaxalone, or tizanidine to ibuprofen does not appear to improve functioning or pain any more than placebo plus ibuprofen by 1 week after an ED visit for acute low back pain.