Duloxetine is an antidepressant medicine. It normally takes 2 to 4 weeks to work. For depression, anxiety and nerve pain, you’ll usually take duloxetine once a day. Duloxetine is used to treat depression and anxiety. In addition, duloxetine is used to help relieve nerve pain (peripheral neuropathy) in people with diabetes or ongoing pain due to medical conditions such as arthritis, chronic back pain, or fibromyalgia (a condition that causes widespread pain).