Intravenous morphine at 0.1 mg/kg is not effective for controlling severe acute pain in the majority of patients

Study objective: The objective was to quantify the analgesic effect of a dose of intravenous morphine, 0.1 mg/kg, to emergency department (ED) patients presenting in acute, severe pain. Methods: This was a prospective convenience cohort of patients aged 21 to 65 years and presenting to an academic urban ED with acute, severe pain. Patients rated their pain intensity on a validated 11-point verbal numeric rating scale ranging from 0, "no pain," to 10, "worst possible pain," immediately before they received 0.1 mg of intravenous morphine per kilogram of body weight and 30 minutes later. The main outcome was proportion of patients whose pain decreased by less than 50% during the 30-minute interval. Results: Of 119 patients who received intravenous morphine at 0.1 mg/kg, the average age was 42 years (SD=11 years), 55% were female patients, 65% were Hispanic, 28% were black, and 7% were classified as other. The median numeric rating scale pain score at baseline was 10 (interquartile range 9 to 10). Sixty-seven percent (95% confidence interval 58% to 76%) of the patients receiving intravenous morphine at 0.1 mg/kg reported a less than 50% decrease in pain. No patient required an opioid antagonist at any time during or after the study period. Conclusion: The data suggest that a 0.1 mg/kg dose of morphine may be too low to adequately control acute severe pain.