The potential impact of pharmacogenetic-guided therapy in a variety of other healthcare settings has been described.9 A trial of CYP2D6-guided pain treatment suggested improved pain control from opioids for patients with chronic pain.10 Acute pain could similarly benefit from more targeted use of medications for more effective pain control in the ED and mitigation of opioid use disorder development.11,12 To our knowledge, ours is the first study focused on EDs, in which we found the top three most frequently prescribed CPIC medications are commonly used for treating pain and nausea. The gene discussed is CYP2D6; the disease is opioid use disorder.