If anyone cares, anal absorbtion is carried by the same vasculature as the stuff you swallow, right up to the ....wait for it.... liver (as many have already said on this string). Injecting bypasses this "first pass metabolism." Now injecting a methyl is just plain stupid for too many reasons to write, not the least of which the binders and impurities in capsules are gonna lodge on heart valves, then you gotta get open heart surgery and feel really silly. But bottom line, don't go shoving pills up your arse, unless you like that better than sipping them with some water. How far must you shove? Above the "dentate line".