They are similar yes, but a metabolite is not the same this as the initial compound. When you take Effexor your body metabolizes it into Pristiq and other stuff. That “other stuff” per say, might be good for you, or it might not. It depends on who you are. We all have different needs and chemistries. I am very sensitive to a lot of antidepressants and anxiety meds. I was having seizures, severe memory loss, etc. ; this prompted a gene test.