Any chance the naproxen sodium was a pain/decongestant combo pill? 5 of those time releasing pseudoephedrine will make your heart pound like crazy, then the anxiety kicks in, and it gets even worse as your monitor it. With really bad flues I have taken 2 of the "cold and sinus" type naproxen with the decongestant every 8 hours, and that is noticeable, but not scary. 3 more certainly would be. This would seem to me more likely than the mix creating a big problem.