Participants randomized to the first group, LDK1, will receive an intravenous injection of low dose ketamine (0.15mg/kg).

All participants, regardless of the group, will receive a dose of morphine(0.15mg/kg) at the same time the study drug is administered.

Participants randomized to the second group, LDK2, will receive an intravenous injection of low dose ketamine (0.3mg/kg).

All participants, regardless of the group, will receive a dose of morphine(0.15mg/kg) at the same time the study drug is administered.

This group will receive a placebo injection of 0.9% normal saline of a similar volume (0.05ml/kg)

0.15mg/kg ketamine delivered IV (in the vein) following clinician assessment in ER. Number of cycles: until discharge or 6 hours elapses.

At baseline, to assess our primary aim, efficacy of pain control, we will use patient reported pain scores and amount of rescue analgesia (parenteral morphine) received. Trained research assistants (RA) will ask participants to report their pains scores using a numerical pain rating scale (NPRS). The NPRS used will be a 0 to 10 rating scale: a rating of 0 corresponds to "no pain at all," whereas a rating of 10 is the "worst pain imaginable." Baseline NPRS will be measured after randomization, but just before administration of ketamine or placebo injection and morphine (Baseline). Repeat measurements will be taken at 15 minutes, 30 minutes, and hourly following treatment with the study drug, for 6hrs or until the patient leaves the ED. The amount of rescue analgesia will be recorded at each time point. The ED course will also be reviewed post hoc by the RAs and physician investigators to confirm analgesia received. The main outcome measure will be the change in pain score over time.

Adverse events will further be defined as Hypotension (SBP < 90), Hypertension (SBP >180, or Diastolic Blood Pressure >110), Presence of nausea/vomiting, presence of hallucinations, Respiratory depression (pOx<92%, Respirator Rate<12, EtCO2 >40), and need for naloxone. All patients will be monitored continuously with cardiac telemetry, pulse oximetry, and capnography following administration of the study drug. Level of sedation will be assessed using an adaptation of the Ramsay Scoring System and the Pasero Opioid Induced Sedation Scale. (Appendix 2) Further, the ED and inpatient course will be reviewed post hoc by the RAs and physician investigators who will record: Time to inpatient admission or discharge, inpatient length of stay, time to operative intervention, outcome of admission (i.e. discharge to home, SNF, rehab) and any morbidity and mortality suffered by the patient and medical complications (myocardial infarction, respiratory infection, etc…).