The combination of naproxen with skeletal muscle relaxants, such as orphenadrine or methocarbamol, is not superior to naproxen alone or placebo in patients with low back pain who are admitted to the emergency department, according to findings from a randomized double-blind trial published in the Annals of Emergency Medicine.
For this comparative trial, researchers assessed the functional outcomes in patients with acute, non-radicular, non-traumatic low back pain receiving naproxen plus placebo (n=79), naproxen plus orphenadrine (n=80), or naproxen plus methocarbamol (n=81). The primary outcome was improvement on the Roland-Morris Disability Questionnaire (RMDQ) at 1 week compared with baseline.
Participants taking naproxen plus placebo experienced a 10.9-point improvement in mean RMDQ score (95% CI, 8.9-12.9). In comparison, participants receiving naproxen plus orphenadrine had a 9.4-point improvement (95% CI, 7.4-11.5) and patients receiving naproxen plus methocarbamol experienced an 8.1-point improvement (95% CI, 6.1-10.1) in mean RMDQ score. The investigators found no statistically significant between-group differences.
Adverse events were more frequently reported by patients receiving naproxen plus methocarbamol (19%) vs patients receiving naproxen plus placebo (17%), and naproxen plus orphenadrine (9%).
According to the investigators, this study may have had a level of selection bias, particularly as patients with chronic low back pain were excluded from the study. Therefore, these results may not be generalizable to patients with other types of low back pain.
The results of this trial concur with previous research, “suggesting that, in general, combinations of medications do not improve low back pain.”
Friedman BW, Cisewski D, Irizarry E, et al. A randomized, double-blind, placebo-controlled trial of naproxen with or without orphenadrine or methocarbamol for acute low back pain. Ann Emerg Med [published online October 28, 2017]. doi:10.1016/j.annemergmed.2017.09.031