Objective To assess the effect of a single dose of intravenous dexamethasone in addition to routine treatment on visual analogue scale (VAS) pain scores at 24 h in emergency department (ED) patients with low back pain with radiculopathy (LBPR).

Methods Double-blind randomised controlled trial of 58 adult ED patients with LBPR, conducted in one tertiary and one urban ED. The intervention was 8 mg of intravenous dexamethasone (or placebo) in addition to current routine care. The primary outcome was the change in VAS pain scores between presentation and 24 h. Secondary outcomes included VAS pain scores at 6 weeks, ED length of stay (EDLOS), straight leg raise (SLR) angles and Oswestry functional scores.

Results Patients treated with dexamethasone had a 1.86 point (95% CI 0.31 to 3.42, p=0.019) greater reduction in VAS pain scores at 24 h than placebo (dexamethasone: −2.63 (95% CI −3.63 to −1.63) versus placebo: −0.77 (95% CI −2.04 to 0.51)). At 6 weeks, both groups had similar significant and sustained decrease in VAS scores compared with baseline. Patients receiving dexamethasone had a significantly shorter EDLOS (median: 3.5 h vs 18.8 h, p=0.049) and improved SLR angle at discharge (14.7°, p=0.040). There was no difference in functional scores.

Conclusions In patients with LBPR, a single dose of intravenous dexamethasone in addition to routine management improved VAS pain scores at 24 h, but this effect was not statistically significant at 6 weeks. Dexamethasone may reduce EDLOS and can be considered as a safe adjunct to standard treatment.

Trial registration number ACTRN12611001020976.