I exclusively use Osco-brand "Tussin" Cough syrup, 350mg DXM HBr in a 4oz bottle. It gets me well fucked up, never any negative side-effects (though I may just have a strong stomach and a knack for exploiting a high, I dunno), and is as safe as you can get when taking it in the syrup form (Dextromethorphan is the ONLY active ingrediant). I wouldn't mind taking Robitussin Maximum Strength Cough either, it's basically the commercial version of the generic "Tussin" cough, or anything else with Dextromethorphan as the only active ingrediant would be safe, assuming you don't take more than 2000mg of the DXM (which would require drinking almost 3-8oz bottles... good luck with that). I can't speak for DXM in pills, never found any sources with DXM-only (NEVER take CCCs, they're appealing because they don't have that horrible syrup taste, but they literally fuck up your system with CPM).