Duloxetine is a selective serotonin and norepinephrine reuptake inhibitor (SNRI) used to manage major depressive disorder, generalized anxiety disorder, diabetic nerve pain, and fibromyalgia. It functions by increasing serotonin and norepinephrine levels in the brain to modulate mood and pain. It is typically taken once daily, with or without food, and may take 2–4 weeks to show effectiveness.