Cymbalta^® (duloxetine hydrochloride) is licensed to treat several conditions, including depression, neuropathic pain, fibromyalgia, and generalized anxiety disorder. Most people tolerate Cymbalta well. However, side effects are possible and may include nausea, drowsiness, and dizziness. This prescription medication works by affecting certain chemicals in the brain, including serotonin and norepinephrine. The medication comes in the form of a capsule and is taken once or twice a day.