Study objective The objective of this study was to determine the analgesic efficacy and safety of intravenous, single-dose paracetamol versus dexketoprofen versus morphine in patients presenting with mechanical low back pain (LBP) to the emergency department (ED).

Methods This randomised double-blind study compared the efficacy of intravenous 1 gm paracetamol, 50 mg dexketoprofen and 0.1 mg/kg morphine in patients with acute mechanical LBP. Visual analogue scale (VAS) was used for pain measurement at baseline, after 15 and after 30 min.

Results A total of 874 patients were eligible for the study, and 137 of them were included in the final analysis: 46 patients from the paracetamol group, 46 patients in the dexketoprofen group and 45 patients in the morphine group. The mean age of study subjects was 31.5±9.5 years, and 60.6% (n=83) of them were men. The median reduction in VAS score at the 30th minute for the paracetamol group was 65 mm (95% CI 58 to 72), 67 mm (95% CI 60 to 73) for the morphine group and 58 mm (95% CI 50 to 64) for the dexketoprophen group. Although morphine was not superior to paracetamol at 30 min (difference: 3.8±4.9 (95% CI −6 to 14), the difference between morphine and dexketoprofen in reducing pain was 11.2±4.7 (95% CI 2 to 21). At least one adverse effect occurred in 8.7% (n=4) of the cases in the paracetamol group, 15.5% (n=7) of the morphine group, and 8.7% (n=4) of the dexketoprophen group (p=0.482).

Conclusions Intravenous paracetamol, dexketoprofen and morphine are not superior to each other for the treatment of mechanical LBP in ED.