there is no rush from IV methadone. and yes, benzo and methadone is dangerous. but if you're just taking your normal dose of methadone that you're already used to and not even getting a buzz from, that 1mg of alprazolam isn't gonna kill you. it'll just add to it, and give you the buzz that you are seeking.
trust me,I'm all about harm reduction, I wouldn't tell you to take a dose that would kill you or put you anywhere near it. now, back in the day before I really had a strong tolerance, I did 90mg of methadone, which was enough to get me high, then I ate 3 bars on top of it. very fuckin' stupid, and I dont' know how I lived. but, for my stupidity, I was punished. I now hae a felony on my record and spent a month in jail because of it.
in fact, it still takes a little bit to kick in, not as long as oral methadone, but not quick enough to shoot it, as there is no rush whatsoever.