O-Desmethylvenlafaxine is primarily used in the treatment of major depressive disorder and anxiety disorders. It functions as an active metabolite of venlafaxine, contributing to the therapeutic effects by inhibiting the reuptake of serotonin and norepinephrine in the brain. This dual action helps to balance mood and alleviate symptoms of depression and anxiety. It is often prescribed when patients require a sustained and balanced approach to managing these conditions, especially in cases where other treatments have not been effective. Additionally, it may be used off-label for managing certain types of chronic pain and neuropathic conditions due to its influence on neurotransmitter activity.