Hi,
I've been on Venlafaxine since late November. I started on 37.5 and moved up to 150 in the first month, stayed there until Feb when I was very quickly bumped up to 300.
Frankly my experience has been FANTASTIC! (hands up who is feeling great these days :-) )
Personally (remembering that everyone is different!) it only helped a little until I hit 300 and then WOW!, within a week I was feeling so very much better.
With regards to side effects, I've had a few, generally when I have increased doses and they have only lasted a few days (headaches, yawning etc). My only big problem has been a bit of "gastrointestinal slowing" but I have found my increased appetite and taking a bucket load of fibre and some docusate has helped a lot.
I've read a lot about the withdrawal, but I suppose I won't know until I go off the drug. My GP has suggested a very long and slow decrease in a year or so, and personally at this stage either a bad withdrawal or a life on Venlafaxine is a lot better then experiencing depression again.
Good luck with the switch over, I hope you feel better soon.
And I hope that if you do get any side effects they don't last long.
