Had terrible side effects from Topomax. stomach ache, nausea, stomach cramps, weight loss, tingling feeling in hands and toes, slight depression, change in taste... and the migrains didn't go away.
I did start with a low dose and slowly increased, so that wasn't the answer.
I tried beta blockers and it didn't help (I have slightly high BP anyway), then my Gastroenterologist switched me from beta blocker to calcium channel blockers for my esophageal spasms, and I haven't had a migraine in about 3 months!
I still get ocassional headaches, but they're not migraines, and tylenol usually takes care of them.
My Dr never suggested antihistamines, worth a try!
Best of luck!
Spasms are bad...