The addition of skeletal muscle relaxants such as baclofen, metaxalone, or tizanidine to an ibuprofen regimen may not further alleviate acute low back pain or improve functioning, according to a study published in Annals of Emergency Medicine.

A total of 320 patients who presented at 1 of 2 emergency departments with nonradicular low back pain were randomly assigned to receive 21 tablets of ibuprofen 600 mg plus baclofen 10 mg, metaxalone 400 mg, tizanidine 2 mg, or placebo (3 daily doses as needed, 7-day supply).

The primary outcome of this randomized placebo-controlled trial was score change between baseline and 1-week follow-up on the Roland-Morris Disability Questionnaire (24-point scale) for functional impairment associated with low back pain; secondary outcomes included pain intensity at the 1-week follow-up.

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Median score at baseline on the Roland-Morris Disability Questionnaire was 19. After 1 week of treatment, participants had a mean overall improvement of 10.8 points on the questionnaire, with average improvements of 11.1, 10.6, 10.1, and 11.2 in patients receiving placebo, baclofen, metaxalone, and tizanidine, respectively, in addition to ibuprofen.

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At the 1-week follow-up, 30% of patients treated with placebo reported moderate to severe low back pain compared with 33%, 37%, and 33% of patients treated with baclofen, metaxalone, and tizanidine, respectively.

Study limitations include that medication doses were not based on previous dose-finding studies, which may have resulted in underdosing.

“Compared with ibuprofen plus placebo, adding baclofen, metaxalone, or tizanidine to ibuprofen does not improve functioning or pain by 1 week after an emergency department visit for acute low back pain,” concluded the study authors.

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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 [published online April 5, 2019]. Ann Emerg Med. doi:10.1016/j.annemergmed.2019.02.017