It is incredibly,
incredibly dangerous to mix benzodiazepines (Xanax, Ativan, etc.) with Methadone. This is common knowledge amongst opiate addicts, at least everywhere I ever went in the US back in my wilder days. I have 3 close friends whom I grew up with that all died before age 30 from abusing that exact combination of narcotics, and know of countless more just in my home state alone.
Benzos are a respiratory depressant, and when combined with Methadone it amplifies it to the point where you stop breathing in your sleep and never wake up from respiratory failure, lack of oxygen to the brain, or your body freaks out and has a coronary episode, etc. it's really really risky -- no joke & no exaggeration. If alcohol is in the mix too then it's even worse.
And I'm not going to pretend like it's not enjoyable -- because it is. It's a great fuckin' buzz if downers are your thing. IMO it's better than heroin (no 'rush' to it, but the effects hit you like a ton of bricks and it lasts all night long. And it's a cheap buzz too), but it's also asking for your life to end.
methadone clinics know this and every one that I've ever seen, heard of, or been to personally Benzos are their one big 'no-no' [as in: if we find it in your Whiz Quiz we kick you out, some won't even give you a second chance and most clinics have mandatory urine screening twice a month, some every week]. You can test positive for damn near anything else -- and they expect you to test positive for opiates -- but if you have benzos in there then you kick rocks.