Low-dose naloxone does not improve morphine-induced nausea, vomiting, or pruritus.

Objective: We tested the hypothesis that low-dose naloxone delivered with intravenous (IV) bolus morphine to emergency department patients in pain would reduce nausea.

Methods: Randomized, double-blind, placebo-controlled trial. Patients receiving 0.10 mg/kg morphine IV bolus rated pain, nausea, and pruritus on 100-mm visual analog scales at enrollment and 20 minutes. Patients were randomized to 0.25 microg/kg naloxone or equal volume placebo administered with IV morphine.

Results: One hundred thirty-one enrolled, 99 (76%) treated according to protocol with sufficient data for analysis. At 20 minutes the difference between groups (naloxone-placebo) was 1 mm (95% CI [confidence interval], -9 to 11) for nausea, 1 mm (95% CI, -3 to 3) for pruritus, 4% (95% CI, -1 to 9) for vomiting, and 0% (95% CI, -5 to 5) for rescue antiemetics. Pain was significantly reduced in both groups.

Conclusion: Addition of 0.25 microg/kg naloxone to bolus morphine does not improve nausea, pruritus, vomiting, or reduce use of rescue antiemetics when administered to emergency department patients in pain.