My husband has been on this med for almost 4 yrs. Since they changed it about a year ago, it does not work as well,, and in the the past few months he has developed a problem he has never had... A headache that will not go away. We have been to neurologist and had mri, ct's, bloodwork, etc.. they can find nothing wrong. So we have went back to what is he doing dailey that could cause the problem.. we can only think of it being this medication... He has never had headaches before, he is almost 45 ... Any one have an answer or any idea's? The neurologist actually said it was prob a migraine., but they really did not think so.. they don't know what it is... but I know they do NOT last for months non stop. I know. I have had them for years. He has to take this med for degenerative disc , 2 cervical fusions(with cages, screws, rods), a thoracic fusion. He also has severe arthritis (he takes the med mobic 4 it) , but continues to push thru and work to support his family. But this headache has stopped him in his tracks. It's going on 2 months now and the headache will not go away... could it be the medicine? Thank you... Any help would be greatly appreciated.