Effexor is a brand-name formulation of the serotonin-norepinephrine reuptake inhibitor (SNRI) medication venlafaxine. SNRIs are typically prescribed to manage symptoms of depression.Effexor and its generic form venlafaxineare prescribed to treat depression, generalized anxiety disorder (GAD), panic disorder, and social anxiety disorder. It is marketed as both an extended-release once-daily medication and as a formulation that needs to be taken two or three times a day.Effexor works by interacting with brain chemistry, changing levels of neurotransmitters that regulate mood and energy, like serotonin and norepinephrine. When taken regularly, these alterations to brain chemistry are expected.It often takes several weeks, and sometimes up to two months, for the medication to take full effect.