Randomized Clinical Trial of Intravenous (IV) Acetaminophen as an Adjunct to IV Hydromorphone for Acute Severe Pain in Emergency Department Patients.

Background: A fundamental challenge for emergency department (ED) clinicians is to relieve severe, acute pain while simultaneously avoiding adverse events associated with opioid analgesics. Because there is evidence that intravenous (IV) acetaminophen is an effective adjuvant analgesic in postoperative settings, we examined whether it also has a role in the ED.

Methods: This was a two-arm, double-blind randomized clinical trial. All patients received 1 mg of IV hydromorphone. Patients were then randomized to receive 1 g of IV acetaminophen or placebo. The primary outcome was the between-group difference in change in pain from baseline (before treatment) to 60 minutes after administration of study drugs, measured on an 11-point numeric rating scale (NRS).

Results: Of 828 patients screened, 162 were enrolled and 159 had the primary outcome. Patients allocated to acetaminophen + hydromorphone had a mean decline in pain from baseline to 60 minutes of 6.2 NRS units; those receiving placebo + hydromorphone had a mean decline of 5.4, a difference of 0.8 NRS units (95% confidence interval [CI] = -0.01 to 1.8). Two patients in each group received additional analgesics in the first 60 minutes of the study. At 120 minutes the NRS pain difference was 0.6 (95% CI = -0.4 to 1.6). A total of 26.9% of patients who received acetaminophen wanted more analgesia versus 37.7% of those given placebo (difference = -10.8%, 95% CI = -24.3% to 4.4%). The incidence of adverse effects was similar in both groups.

Conclusions: The addition of 1 g of IV acetaminophen to 1 mg of IV hydromorphone provided neither clinically meaningful nor statistically superior analgesia than hydromorphone alone.