Participants will be eligible to take duloxetine/placebo if insufficient relief of pain after using naproxen for 48 hours has been reported.
This research study will help determine whether a medication called duloxetine can improve back pain. It is well documented that many participants who come to the ER with acute low back pain still have low back pain 3 months later. The investigator team will attempt to determine whether duloxetine can help prevent this.