Has anyone had success using this to help with Effexor XR (or any other drug) withdrawal?

havent heard of this use

I would suggest going to Kelly's St. John's Wort forum (I don't know the URL -you can do a search for it). There's a whole section on there for 5HTP. I was on 5HTP for two years and it did help with minor depression, but I found anti-depressants to be more helpful with major anxiety and depression. Unfortunately they have more side effects than 5HTP. I wish I could have stayed on 5HTP, as there were virtually no side effects!