Yeah there's a few, expect to visit the toilet on a regular basis, and you'll also retain water of you don't drink enough. Socialising can be a little awkward, and doing anything that requires broad rather than narrow focus (eg driving) can be a bit more difficult. I find my short term memory actually gets better, as does my ability to learn things long term.

I take it whenever I feel like I need a boost of concentration, it usually lasts about 6-8 hours so the latest I'll take it is 6pm if I want to sleep that night.