PURPOSE: Midazolam comedication with morphine is a routine practice in pre and postoperative patients but has not been evaluated in prehospital setting. We aimed to evaluate the comedication effect of midazolam in the prehospital traumatic adults. METHODS: A prehospital prospective randomized double-blind placebo-controlled trial of intravenous morphine 0.10 mg/kg and midazolam 0.04 mg/kg vs morphine 0.10 mg/kg and placebo. Pain assessment was done using a validated numeric rating scale (NRS). The primary end point was to achieve an efficient analgesic effect (NRS≤3) 20 minutes after the baseline. The secondary end points were treatment safety, total morphine dose required until obtaining NRS≤3, and efficient analgesic effect 30 minutes after the baseline. FINDINGS: Ninety-one patients were randomized into midazolam (n=41) and placebo (n=50) groups. No significant difference in proportion of patients with a pain score≤3 was observed between midazolam (43.6%) and placebo (45.7%) after 20 minutes (P=.849). Secondary end points were similar in regard with proportion of patients with a pain score≤3 at T30, the side effects and adverse events except for drowsiness in midazolam vs placebo, 43.6% vs 6.5% (P<.001). No significant difference in total morphine dose was observed, that is, midazolam (14.09 mg±6.64) vs placebo (15.53 mg±6.27) (P=.315). CONCLUSIONS: According to our study, midazolam does not enhance pain control as an adjunctive to morphine regimen in the management of trauma-induced pain in prehospital setting. However, such midazolam use seems to be associated with an increase in drowsiness.