I'm on levetiracetam 500mg twice a day, topamax (topiramate) 100mg once at night and trazodone 100mg at night for chronic migraines. now i'm having constipation?

Wow!: First, are your migraines controlled with all of these medicines? If not, and you are having adverse events, would first modify the above drugs. Topamax (topiramate) works best taken twice daily, and the dose needed may be a bit higher. I do not find migraine helped by Levetiracetam or trazadone usually, and there are many other choices which work far better. Re constipation, increase your dietary fibre.