Can u take just one topiramate instead of two at twelve hr intervals ( as only get headaches at night ) ?

Typically 2x daily: Typically, Topiramate (Topamax) is given at 12 hr intervals. Not to say that it's wrong to give 2 at a time but it's less likely to have the same medicinal effects once daily vs. twice. Remember, this medication PREVENTS headaches from occurring. Therefore, with twice daily dosing likely superior in effect to once it won't matter when your headaches typically appear.

Twice per day better: The half life is 10-12 hours, hence two times per day is a better strategy for headache prevention. The recommended starting dose is 15-25 mg at night increasing very slowly to a total daily dose 400 mg/day in two divided doses. Do not use Acetaminophen more than 12 times per month to avoid medication overuse headache. Good luck.