DLX CAPSULES : Duloxetine is used to treat depression and generalized anxiety disorder (GAD; excessive worry and tension that disrupts daily life and lasts for 6 months or longer). Duloxetine is also used to treat pain and tingling caused by diabetic neuropathy (damage to nerves that can develop in people who have diabetes) and fibromyalgia (a long-lasting condition that may cause pain, muscle stiffness and tenderness, tiredness, and difficulty falling asleep or staying asleep).