Objective To determine the analgesic efficacy and safety of intravenous single-dose paracetamol versus morphine in patients presenting to the emergency department with renal colic.

Methods A randomised double-blind study was performed to compare the efficacy of intravenous paracetamol (1 g) and 0.1 mg/kg morphine in patients with renal colic. The efficacy of the study drugs was measured by a visual analogue scale and a verbal rating scale at baseline and after 15 and 30 min. The adverse effects and need for rescue medication (1 μg/kg intravenous fentanyl) were also recorded at the end of the study.

Results 133 patients were eligible for enrolment in the study, with 73 patients included in the final analysis (38 in the paracetamol group and 35 in the morphine group). The mean±SD age of the subjects was 30.2±8.6 years and 51 (70%) were men. The mean reduction in scores at 30 min after study drug administration was 63.7 mm (95% CI 57 to 71) for paracetamol and 56.6 mm (95% CI 48 to 65) for morphine. The difference between pain reduction scores for the two groups at 30 min was 7.1 mm (95% CI −18 to 4), demonstrating no statistical or clinical significance. Two adverse events (5.3%) were recorded in the paracetamol group and five (14.3%) in the morphine group (difference 9%, 95% CI −7% to 26%).

Conclusion Intravenous paracetamol is effective in treating patients presenting with renal colic to the emergency department.

Clinical trials registration no ClinicalTrials.gov ID number NCT01318187.