Clinical Question

Is treatment for acute low back pain more effective with a combination of ibuprofen and a muscle relaxant compared with ibuprofen alone to improve functional outcomes and reduce pain?

Bottom Line

Adding a muscle relaxant to treatment with ibuprofen does not improve functional outcomes or pain, or lessen the number of people reporting moderate to severe back pain one week after starting treatment. (Level of Evidence = 1b)

Synopsis

The researchers enrolled 320 patients who presented to one of two emergency departments with nonradicular low back pain of two 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 600 mg of ibuprofen to be taken up to three times per day, as needed. They were also randomized, concealed allocation unknown, to receive identical-appearing capsules containing placebo, 10 mg of baclofen (Lioresal), 400 mg of metaxalone (Skelaxin), or 2 mg of tizanidine (Zanaflex) and were instructed to take one or two capsules up to three times per 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.

Study design: Randomized controlled trial (double-blinded)

Funding source: Government

Allocation: Uncertain

Setting: Emergency department

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.

Editor's Note: Dr. Shaughnessy is an assistant medical editor for AFP.