I agree with Beth (as I usually do). If the job involves public safety, like driving a bus, or operating dangerous machinery, such as a meat slicer or lathe, I could understand a question like "are you currently taking any medications that could impair your ability to do your job safely?" However, just to ask outright without relating it to a particular job requirement is, in my mind, problematic at best. Especially if you are just in the application or interview stage.