Throwaway for obvious reasons - me and a bunch of people I went to high school with did pretty frequent and sometimes high doses of this stuff. Rather fun - when you weren't puking your guts out. None of us seem to have come out of it terribly worse for the wear, though there are certainly some horror stories you can read about out there. Plenty of trip reports on Erowid.
In the spirit of harm reduction - you have to be very careful if you decide you're going to (ab)use this stuff OTC to make sure you're not getting any other drugs along with it like acetaminophen, Guaifenesin, chlorpheniramine, pseudoephedrine, or any other active ingredients. They can do permanent damage to various organs or cause very unpleasant effects.