Chronic pain is an enormous problem and there an urgent need to find both alternatives to opioid pain medications and medications that prevent pain from becoming chronic. The ATTAC-Pain (Altering The Transition from Acute to Chronic Pain) study proposes to examine whether duloxetine (a medication that is marketed for depression, anxiety, and specific types of pain conditions), can reduce acute and chronic pain among adults who come to the emergency department (ED)with muscular pain (such as neck pain after a car accident or low back pain). Investigators will enroll 60 patients who come to the ED. Patients will be eligible if they report moderate to severe muscular pain (such as pain in the back, neck, or shoulders). Consenting patients will be randomized to receive duloxetine 30mg, duloxetine 60mg, or placebo (2/3rd chance of being in one of the duloxetine groups). The study team will follow patients for six weeks and collect information on pain outcomes and use of pain medications. Investigators aim to determine if duloxetine can (1) reduce acute pain symptoms following the ED visit, (2) prevent the transition to persistent pain (having pain 6 weeks after the initial ED visit), and (3) decrease opioid use following a motor vehicle collision (MVC). The results of this study will ultimately help determine if duloxetine can be used as a non-opioid pain treatment option that reduces acute pain and prevents the transition to chronic pain. This in turn can improve recovery, reduce opioid use and its consequences, and decrease health care costs.