BACKGROUND:Numerous drugs have been proposed to alleviate pain in patients with biliary colic, especially opioids, but still there is a tendency to use less narcotics because of their side effects and the unwillingness of some patients. The present study aimed to compare the analgesic effect of paracetamol combined with low-dose morphine versus morphine alone in patients with biliary colic. METHODS:A randomized double-blind controlled trial was performed in 98 patients with biliary colic, recruited from two emergency departments from August 2012 to August 2013. Eleven patients were excluded and the remaining were randomized into two groups:group A received 0.05 mg/kg morphine+1000 mg paracetamol in 100 mL normal saline and group B received 0.1 mg/kg morphine+normal saline (100 mL) as placebo. Pain scores were recorded using visual analogue scale (VAS) at baseline and 15 and 30 minutes after drug administration. Adverse effects and the need for rescue medication (0.75 μg/kg intravenous fentanyl) were also reported within 60 minutes of drug administration. RESULTS:Before the infusion, the mean±SD VAS scores were 8.73±1.57 in group A and 8.53±1.99 in group B. At 15 minutes after drug administration, the mean±SD VAS scores were 2.16±1.90 in group A vs. 2.51±1.86 in group B; mean difference was –0.35, and 95％CI–1.15 to 0.45 (P=0.38). At 30 minutes the mean±SD VAS scores were 1.66±1.59 in group A vs. 2.14±1.79 in group B; mean difference was –0.48, and 95％CI –1.20 to 0.24 (P=0.19). The mean pain scores in the two groups at 15 and 30 minutes demonstrated no significant difference. CONCLUSION:Paracetamol combined with low-dose morphine may be effective for pain management in patients with biliary colic.