No short-term extra benefit when muscle relaxants are added to ibuprofen for acute low back pain

Reference

Friedman BW, Irizarry E, Solorzano C, et al. A randomized, placebo-controlled trial of ibuprofen plus metaxalone, tizanidine, or baclofen for acute low back pain. Ann Emerg Med 2019;74(4):512-520.

Synopsis

These researchers enrolled 320 patients who presented to 1 of 2 emergency departments with nonradicular low back pain of 2 weeks' duration or less (average 72 hours) with a score of at least 6 of a possible 24 on the Roland-Morris Disability Questionnaire, a self-rated measure of disability due to low back pain. More than 90% of patients had a score of 10 or higher. All patients were given ibuprofen 600 mg to be taken up to 3 times a day, as needed. They were also randomized, concealed allocation unknown, to receive identical-appearing capsules containing placebo, baclofen 10 mg, metaxalone 400 mg, or tizanidine 2 mg, and were instructed to take 1 or 2 capsules up to 3 times a day, as needed. One week later, using intention-to-treat analysis, questionnaire scores improved in all groups, with improvement ranging from an average 10.1 points to 11.2 points across the groups compared with baseline. At this time, approximately 34% of patients across the groups reported moderate to severe back pain. The study had a power of 80% to find a difference of 5 points on the questionnaire if one existed.