From crazymeds.us (excellent site for info

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Topamax's Pros: It's the currently the only "modern" anticonvulsant approved by the FDA that you can take by itself to treat tonic-clonic (or clonic-tonic as the case may be) complex partial seziures and simple partial seizures. By "modern" Ortho-McNeil means "approved after 1995 and sucks less than Depakote." I'm getting lots of e-mails and reading numerous reports of people getting relief from their migraines at just 25mg a day. You're more likely to lose weight than gain weight (although this is a bug, not a feature, for me and a few other people). The best med on the market for temporal lobe dysfunctions. It really helps with the sensory integration problems in autism.
Topamax's Cons: If you don't have a temporal lobe dysfunction or problems with other parts of your brain that Topamax hits, or you're at the wrong dosage, it will make you dumber than a box of rocks. The kidney stones aren't much fun. Because it was newly approved for migraines and can work at a low dosage without all the sucky side effects of Depakote (Who cares if you're stupid as long as you're not fat and don't need blood work?) the pharmaceutical reps are pressuring the doctors to prescribe it to anyone and everyone with bad head pain, even if it's not appropriate. New Approval Syndrome can thus screw people by prescribing them the wrong drug for their migraines. Worse yet when they may not even have migraines, and perhaps have trigeminal neuralgia, for which Tegretol is more appropriate.
Topamax's Typical Side Effects: The usual for anticonvulsants. A pins & needles effect that usually goes away after no more than a week or two. Weight loss and appetite suppression - but please note that not everyone gets this side effect. Sodas and other carbonated beverages will utterly taste like ***, so you may as well give them up now if you're considering Topamax. Memory loss, aphasia (weird words coming out in place of what you meant to say or write), word find problems (not being able to recall the names of people, things or concepts), and a general cognitive impairment that has earned this drug the nicknames "Stupamax" and "Dopamax." As Topamax typically makes you really sleepy and has a long enough half-life, you can usually get away with taking it all at bedtime.
Topamax's Not So Common Side Effects: Dry and/or itchy eyes along with assorted vision problems. Topamax also has a warning for rare forms of myopia and glaucoma, so if you get any sort of visual weirdness, have your eyes checked immediately! Fortunately discontinuing Topamax usually takes care of these issues, but you can't let your doctor just blow it off as an eye thing. You may find yourself not able to drink coffee any more, so be prepared to quit the bean. Because it does hit the temporal lobes so hard you can get a zombification effect that is typically experienced only with antipsychotics. Unlike the antipsychotics it's not such a sure thing it will go away in a matter of a couple of weeks. And since the olfactory bulb is wedged in that neighborhood, food in general, and not just carbonated beverages, may not taste quite the same. If you were experiencing frequent, intense deja vu or jamais vu you might experience the other as the damaged temporal lobe starts working correctly.
Topamax's Freaky Rare Side Effects: Tongue paralysis. Combine that with not being able to get the right words out and you're all set to apply for the position of village idiot. There have also been a couple of men who started lactating after taking Topamax.
Happy reading!