How can i switch from effexor (venlafaxine) xr 150mg to paxil 20mg experiencing no withdrawal?

Would be gradual: I would be more gradual about tapering the effexor, (venlafaxine) since its mechanism is not only with serotonin but also norepinephrine. The process might require a cross-taper from Effexor (venlafaxine) to paxil. This means starting Paxil at a lower dose while gradually decreasing Effexor (venlafaxine) -- eventually moving to Paxil alone. Please work with your psychiatrist on this.