I have RA and have been taking methotrexate and enbrel for several years now. While the enbrel never really lasted throughout the week, it used to go at least 4-5 days before it wore off. NOw, it seems like it only lasts 1-2 days before I start feeling like I've been hit by a truck. I've read somewhere that enbrel (or any of the biologics for that matter) can stop working effectively after a certain period of time. Has this happened to anyone? Fortunately, I have lots of other choices these days (with all of the new drugs out there), but I would prefer not to switch unless I have no choice.