Have you taken effexor (venlafaxine) xr and felt the effects almost immediately?

Yes: Some patients say they have felt a benefit the first day they take a medication. That is likely due to the placebo effect and not the medication itself.You will notice side effects immediately.Depending on the side effect of the medication it can be beneficial, such as having more energy or sleepng better. The medication needs to build up in your system over a few weeks to obtain maximum benefit.