Effexor/Effexor XR was my longest lasting med besides my current meds (Remeron and Topamax, both which I’ve been on for nearly 8 months now); I was on Effexor for exactly 6 months. I never had any noticed side effects from it, and I never experienced immediate withdrawal symptoms after a day of missing a dose. I had severe depression at the time I was on it, so unfortunately however, it never worked for me, despite that I was on its maximum dose at 300 mg (150 mg x 2/twice daily). I hope it works for you though! So also, I had a difficult time weaning my way off it, because also, I would advise you as well that, as previously stated, and as you probably already heard elsewhere, Effexor is one of those meds with a high rate of withdrawal occurrence which can be unpleasant, so also if and when you happen to stop Effexor, I hope you don't encounter its infamous withdrawals! Coming off of Effexor after being on it for 6 months, especially coming off the maximum dose of 300 mg, I did experience those “brain zap” withdrawal symptoms that are kind of difficult to explain; they were sudden, quick jolt-like sensations that went through my head and they were rather startling as they were unexpected and unpleasant and they produced a moment of vertigo and the ground beneath me would seem to whirl and I would seem to slightly lose my balance. Accompanying the "brain zaps", I got those electric shock feelings as well that shot throughout my arms and hands.