I'm not sure about methadone's bioavailability. I know that orally it's very good, but I don't know about rectally. It should at least be on par with oral. Generally rectal administration of drugs has the best bioavailability without injecting it. The onset time should be faster but could still be pretty long. Methadone takes forever to kick in.I have to admit though, I have this thing for putting stuff up my ass lately. By "stuff", I mean drugs, lol. Not dicks or dick-like objects just to be clear. Suboxone films are the best so far. 2mg up the butt is like 4mg under the tongue. Seriously, try it.
A few months back I mixed up a 1mg blue xanny along with about 10 of those 5mg perc IR's with water and pretty much gave myself a drug cocktail enema. It worked pretty good I think. I still haven't gotten around to trying it with methadone. What do you think MrDuck? Would it be worth the effort? I know methadone already has pretty high BA orally. Would I gain anything other than possibly having it kick in quicker?