I've never heard of Tizanidine so I looked it up. Glad I did. According to Wikipedia it belongs to a class of meds called centrally acting (meaning CNS, so neurons likely involved) alpha 2 (a2) andrenergic agonists. Since I have migraines and have tried most migraine preventatives, I'm happy to learn of this. Also my current muscle relaxant is now only available in generic which does not seem to be working. Hmm... It says that alpha 2 receptors are involved in the sympathetic nervous system. It looks like this class of drugs mimics the actions epinephrine (adrenalin) and/or norepinephrine (noradrenalin) in various ways. Agonists increase or inhanse the effect. There is a list of other drugs in the same class so perhaps you should look at others in that category. Maybe you can find one that will work like the tizanidine but without the problems you are having. Perhaps someone with better knowledge of these drugs could comment.