Advil (ibuprofen) migraine says only 2 caps in 24 hrs since it has potassium in it. i took 2 tabs 15 hrs ago w/no relief. can i now take 600mg of regular advil (ibuprofen)?

Yes: Most likely the dose recommendation has nothing to do with potassium. Rather it becomes problematic even after a few days at doses of 2400mg or greater of ibuprofen. Long term doses should always be much less. Magnesium is rather what is used to help treat/prevent migraines. I've really never heard of potassium being used for this.

Yes you can: The maximum single dose of Advil (ibuprofen) is 800mg. as long as it is not taken on an empty stomach. Only it probably will increase your chance of gastro-intestinal bleeding or ulser.