It is a more refined version of venlafaxin/Effexor. The most active component are the same. In pristiq the stereochemical less-active part of the venlafaxin is removed and then it is called desvenlafaxin, it is claimed to make fewer side-effects. It is a way for the drug company to make money after the patent of the venlafaxin is expired. They can claim it is a new drug. Not, really. It might be less effective with the same side-effects.
https://en.wikipedia.org/wiki/Desvenlafaxine
https://en.wikipedia.org/wiki/Desvenlafaxine
