Randomized Clinical Trial of Intravenous Acetaminophen as an Analgesic Adjunct for Older Adults With Acute Severe Pain

Acad Emerg Med. 2019 Apr;26(4):402-409. doi: 10.1111/acem.13556. Epub 2018 Nov 20.


Objectives: Older adults are at risk for undertreatment of pain. We examined intravenous (IV) acetaminophen as an analgesic adjunct to IV opioids in the care of older emergency department (ED) patients with acute severe pain.

Methods: This was a randomized clinical trial conducted in two EDs in the Bronx, New York. Eligible adults aged 65 years and older with acute severe pain were randomized to 0.5 mg of IV hydromorphone and 1 g of IV acetaminophen or 0.5 mg of IV hydromorphone and 100 mL of normal saline placebo. The primary outcome was the between group difference in improvement of numerical rating scale (NRS) pain scores at 60 minutes. Secondary outcomes were the between-group differences in the proportion of patients who chose to forgo additional pain medications at 60 minutes; the proportion who developed side effects; the proportion who required rescue analgesia; and between-group differences in NRS pain scores at 5, 15, 30, and 45 minutes.

Results: Eighty-one patients were allocated to each arm. Eighty patients in the IV acetaminophen arm and 79 patients in the placebo arm had sufficient data for analysis. At 60 minutes, patients in the hydromorphone + IV acetaminophen group improved by 5.7 NRS units while those in the hydromorphone + placebo group improved by 5.2 NRS units, for a difference of 0.6 NRS units (95% confidence interval [CI] = -0.4 to 1.5). A total of 28.7% of patients in the hydromorphone + IV acetaminophen group wanted more analgesia at 60 minutes versus 29.1% in the hydromorphone + placebo group, for a difference of -0.4% (95% CI = -14.3% to 13.5%). These differences were neither clinically nor statistically significant. Safety profiles were similar in both groups.

Conclusion: In this randomized clinical trial, the addition of IV acetaminophen to IV hydromorphone as an adjunctive analgesic for acute, severe, pain in older adults provided neither clinically nor statistically superior pain relief when compared to hydromorphone alone within the first hour of treatment.

Publication types

  • Multicenter Study
  • Randomized Controlled Trial
  • Research Support, N.I.H., Extramural

MeSH terms

  • Acetaminophen / administration & dosage*
  • Acetaminophen / adverse effects
  • Acute Pain / drug therapy*
  • Administration, Intravenous
  • Aged
  • Analgesics, Non-Narcotic / administration & dosage*
  • Analgesics, Non-Narcotic / adverse effects
  • Analgesics, Opioid / administration & dosage
  • Chemotherapy, Adjuvant / methods
  • Double-Blind Method
  • Emergency Service, Hospital
  • Female
  • Humans
  • Hydromorphone / administration & dosage
  • Male
  • Pain Management / methods*
  • Pain Measurement
  • Treatment Outcome


  • Analgesics, Non-Narcotic
  • Analgesics, Opioid
  • Acetaminophen
  • Hydromorphone