285 patients have recruited instead on 496 but we don't want to continue to prolonge the study. Analysis will be performed on the data we have.

This is a prospective, randomized, single-blind trial evaluating prehospital patients experiencing moderate to severe acute pain, defined as a numeric rating scale score greater than or equal to 5. Patients will be randomized to receive ketamine at or morphine by intravenous push.

This study is designed to evaluate if ketamine alone is non inferior to morphine alone for prehospital analgesia. Numeric rating scale pain scores will be compared between recipients of ketamine and recipients of morphine at 15, 30, 45 and 60 min post first injection and at hospital admission.

Inclusion Criteria:

• older than 18 years old
• prehospital moderate to severe acute pain, defined as a numeric rating scale score greater than or equal to 5

Exclusion Criteria:

• unstable vital signs (systolic blood pressure <90 or >200 mm Hg, pulse rate <50 or >150 beats/min, and respiration rate <10 or >30 breaths/min)
• pregnancy
• breast-feeding
• altered mental status
• unable to give numeric rating scale scores
• allergy to morphine or ketamine
• acute pulmonary edema
• acute coronary syndrome
• renal or hepatic insufficiency
• patient who received morphine for the same acute pain
• acute psychiatric illness