Used primarily as an active pharmaceutical ingredient in antidepressants for the treatment of depression. It functions by inhibiting the reuptake of neurotransmitters such as serotonin and norepinephrine in the central nervous system, helping to balance mood-related brain chemicals, thereby reducing symptoms of depression, anxiety, and promoting a sense of relaxation. It is commonly prescribed for patients with chronic or severe depression and must be used under medical supervision due to potential side effects such as drowsiness, dry mouth, or dizziness. Additionally, it serves as a reference standard in analytical testing and quality control within pharmaceutical manufacturing.