I'm with Bavanai on this one. I've done a lot of experimentation with DXM polistirex. If you take enough of it you won't trip for two days, but some of the secondary effects like the body buzz, slight trouble seeing ("lizard eyes"), etc., can persist for at least a day after the primary effects have ended.
I've made it my habit to take 1/4 to 1/3 of any DXM dose in the form of polistirex (Delsym) about 60-90 minutes before I drink my Agent Lemon. I have found that this propels me into an intensely more psychedelic state than just taking the same dose of DXM HBr. I only do DXM at around the high third plateau (12mg/kg), and with this method I've found the hallucinations are a lot more engrossing and the headspace is more epic and shamanic.
The theory behind why this works is pretty simple. It's similar to (but not the same as) a Plateau Sigma trip, wherein you take DXM HBr in staged doses, because DXM metabolizes to DXO, which inhibits CYP2D6 and makes any further DXM you take hit harder. If you take polistirex first, then an hour later you take a large dose of HBr, the latter will really propel you into the trip first, but it will also break down to DXO. As more and more of the polistirex is time released, it hits harder and stretches the trip a bit, but it also has the effect of changing the headspace. It's not as intense as a Plateau Sigma trip, and you can still tell what's real and what's not, but it's different than a normal Third Plateau trip would be.
DXM polistirex has its uses.
