You could grind it up and snort it, or use a measuring syringe, add H2O and after letting it soak for a while, plug the solution ('plug' in that context, means to apply intra-rectally. Of course, the measuring syringe is best off with no needle attached. For obvious reasons. Same bioavailability and speed of onset roughly for a great many drugs as delivery via intramuscular injection, only without the risk of infection if sterility is not practiced. And of course, given what one's arse is usually used for, the presence of bacterial traces is not, exactly, an issue. If you see what I mean. Sticking it up the tradesman's entrance as with injection, with a drug shortens the duration of action but intensifies the effect. Extraction from XR formulations generally means doing a second soak and leaving it so as not to waste any. And go drop one before plugging anything, otherwise...ahem..mechanical absorption in excrement present in the rectum and lowest regions of the bowel can take place and significant wastage (pun intended) can occur. So it should be done with an empty arse. Just take a shit, if you need one. If you can't, then there's generally nothing to worry about. It works just fine with amphetamines. More experience using the mode of application for opioids personally, mainly when my stomach issues have been playing up badly enough it was impossible to swallow anything and with substances with piss-poor bioavailability orally, whence in the former instance had i taken say, my oxy by mouth, and having too large a dose to put up the nose, in terms of a large pile of powder it would have been vomited.)
Takes between 5 and 15 minutes, more like somewhere in the middle of that to begin taking proper effect. Peak effect is higher, duration is shortened. The same goes, whilst I've never done it with amphetamine itself, it works just fine with methamphetamine and is well known to work for plain vanilla amphetamine and a great many other meds and recreationals. Diazepam for instance is made as an emergency anticonvulsant in rectal dosage units containing an emulsion of the benzo, the idea being for the responder to an unconscious patient having a seizure, where it would be difficult or dangerous to try and get a needle in them to administer the anticonvulsant and have it take a similarly rapid effect.)
What form is the dex in? IR or XR? and if its XR, the microbead formulations work the best, and leaching from the substrate once finely ground to powder is more rapid than with tablet forms. Best way to do it, is to suck it through an un-used rollup type cigarette filter, to retain the majority of the ground up matrix. This is not due to any danger from particulates with rectal use, but so that the filter can be returned to the container with the sludge from the XR matrix, more H2O added, 5ml, or 10ml would do just fine, does do just fine in fact, and is not sufficient to cause discomfort. Just keep it in there and let it absorb. The filter on the other hand, after adding more water to it and the remaining matrix in whatever container you did the extraction in, still contains a portion of the XR drug, and that can be left soaking, after squashing it around in say, a mortar and pestle, or if you have not one, then a cup and the handle of a knife, a screwdriver handle, or anything of that nature. Its hardly a technical challenge, if it can squish something about in water, then it'll do, a finger will serve if nothing else is available (into the cup, that is, not up your arse, as cute as I bet it is:))
If your squeamish about a couple of milliliters of water and amphetamine solution being squirted up your chocolate starfish, then just powder, rack up into a couple of lines with a credit card on a smooth surface, mirror, CD case or whatever and rail it with a straw (bank notes, at least the old kind don't have as smooth a surface, and you probably don't want to lick one to get the last traces, considering how many hands they will have passed through, and most likely, how many other noses they have been up before going up that cute little protrusion below your aspie death stare:autism:)
And the shorter the piece of drinking straw, the less powder gets to cover the surface and the more up your nose.
Either way, shorter duration, higher peak effect.
