A multicenter randomized controlled trial published in Annals of Emergency Medicine found that subdissociative-dose ketamine (0.3 mg/kg IV) provided superior pain relief at 30 minutes compared to morphine (0.1 mg/kg IV) for acute musculoskeletal pain in the emergency department, with a more favorable adverse effect profile across 847 patients at 11 academic emergency departments.
Acute musculoskeletal pain — fractures, dislocations, sprains, and soft tissue injuries — is among the most common presentations to emergency departments, accounting for approximately 30 million ER visits annually in the United States. Opioid analgesics have been the standard of care for moderate-to-severe musculoskeletal pain for decades. A new multicenter trial provides the strongest evidence to date that subdissociative-dose ketamine is a superior alternative.
Subdissociative-dose ketamine — typically defined as 0.1 to 0.3 mg/kg IV — has been used as an analgesic in emergency departments since the early 2000s. At these doses, ketamine provides analgesia through NMDA receptor antagonism without the dissociative effects seen at anesthetic doses. It does not cause respiratory depression, does not require opioid receptor activation, and has a favorable hemodynamic profile.
The theoretical advantages of ketamine over opioids for acute pain management are substantial: no respiratory depression, no opioid-related nausea and vomiting, no risk of opioid-induced hyperalgesia with repeated dosing, and no contribution to the opioid epidemic through prescribing or diversion. Several smaller trials and meta-analyses had suggested clinical equivalence or superiority to opioids for various pain types, but a large, well-powered multicenter RCT had been lacking.
The trial enrolled 847 adults presenting to 11 academic emergency departments with acute musculoskeletal pain rated 5 or higher on an 11-point numeric rating scale. Patients were randomized 1:1 to receive either subdissociative-dose ketamine (0.3 mg/kg IV over 15 minutes) or morphine (0.1 mg/kg IV over 15 minutes). Both drugs were administered in identical syringes by blinded research nurses. Patients, treating clinicians, and outcome assessors were all blinded to treatment assignment.
The primary outcome was pain score reduction at 30 minutes, measured on the 11-point numeric rating scale. Secondary outcomes included pain scores at 15, 60, and 120 minutes; rates of rescue analgesia; adverse effects; patient satisfaction; and time to discharge. The trial was powered to detect a minimum clinically important difference of 1.3 points on the numeric rating scale.
At 30 minutes, the ketamine group demonstrated a mean pain score reduction of 4.1 points (from 7.8 to 3.7), compared to 3.2 points in the morphine group (from 7.7 to 4.5). The between-group difference of 0.9 points (95% CI 0.6–1.2, p<0.001) exceeded the pre-specified minimum clinically important difference threshold.
At 60 minutes, the difference between groups had narrowed but remained statistically significant (ketamine 3.1 vs. morphine 3.8, p=0.003). By 120 minutes, pain scores were similar between groups (ketamine 2.9 vs. morphine 3.1, p=0.21), suggesting that morphine's slower onset accounts for much of the early difference.
Rescue analgesia was required in 18% of the ketamine group versus 29% of the morphine group (p<0.001), indicating that ketamine's superior early analgesia translated into clinically meaningful reductions in the need for additional pain medication.
The adverse effect profile strongly favored ketamine. Nausea occurred in 8% of the ketamine group versus 24% of the morphine group (p<0.001). Vomiting occurred in 3% versus 11% (p<0.001). Oxygen desaturation (SpO2 <94%) occurred in 1% of the ketamine group versus 6% of the morphine group (p=0.001).
Ketamine-specific adverse effects were mild and transient. Dizziness occurred in 22% of the ketamine group versus 14% of the morphine group (p=0.002). Dysphoria or unpleasant feelings occurred in 11% of the ketamine group versus 4% of the morphine group (p<0.001). No patient in either group experienced a serious adverse event requiring intervention beyond observation.
Patient satisfaction scores were similar between groups (ketamine 8.2/10 vs. morphine 7.9/10, p=0.09), suggesting that ketamine's higher rate of dysphoria did not translate into lower overall patient satisfaction — likely because the superior analgesia offset the unpleasant side effects.
| Outcome | Ketamine | Morphine | p-value |
|---|---|---|---|
| Pain reduction at 30 min | 4.1 pts | 3.2 pts | <0.001 |
| Rescue analgesia required | 18% | 29% | <0.001 |
| Nausea | 8% | 24% | <0.001 |
| Vomiting | 3% | 11% | <0.001 |
| O2 desaturation | 1% | 6% | 0.001 |
| Dizziness | 22% | 14% | 0.002 |
| Dysphoria | 11% | 4% | <0.001 |
| Patient satisfaction | 8.2/10 | 7.9/10 | 0.09 (NS) |
The trial's findings are particularly significant in the context of the ongoing opioid epidemic. Emergency departments are among the largest prescribers of opioid analgesics in the United States, and ER opioid prescriptions have been identified as a gateway to opioid use disorder in a subset of patients. A shift toward ketamine for acute musculoskeletal pain management could reduce ER opioid prescribing without compromising — and potentially improving — pain control.
The CDC's updated opioid prescribing guidelines, released April 24, 2026, explicitly endorse multimodal analgesia as first-line therapy for acute pain in the emergency department and identify ketamine as an appropriate component of multimodal regimens. The Annals trial provides the randomized evidence base that the CDC guidelines reference.
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