Unfortunately I have a lot of experience with mixing methadone & alchohol.
My addict was a long term IV heroine user. About 6 or 7 years ago she stopped using heroine (from what she told me- I dont really know for sure) and started going to a methadone maintenance clinic. She is on a high daily dose.
She didnt disclose to me about the methadone clinic until about 6 months into our relationship. After she told me, I started reading a lot about methadone & methadone clinics.
Methadone is a nervous system depressent. Alcholhol is also a depressent. Its published all over the internet concerning the dangers of mixing the two drugs. The alchohol can also speed up the metabolism which causes methadone to be proceesed through the sysytem faster. Due to both being depressants the heart & breathing can be slowed to dangerous & possibly deadly levels. Reaction times are slowed. Driving can be very dangerous.
My addict drank morning noon & night. Initially, I knew about the drinking & didnt know about the methadone. After I read online & learned about methadone I was extremely concerned for her safety. I tried on many occasions to talk to her about it but that went no where. Her response was always "she liked the buzz from the alchohol".
My addicts requirement to be on a high daily dose of methadone has to be in part due to the methadone & alchohol mixture causing the methadone to leve the body faster than just taking methadone alone.
Methadone is an extremely powerful drug. In my addicts case she is not in recovery. Its just a continuance of her addiction. She suffers from numerous bad side effects. I was not able to understand any of it until she told me about the MMT & I began reading online. From that reading I came to understand her in ways she could have never explained to me.
There is tons of quality information published online concerning methadone. A lot of very sound scientific medical studies. Methadone related deaths across the country are on the rise. Methadone when abused is very dangerous.
When used the right way in a legit clinical program which contains close monitoring, regular drug testing, a recovery plan, medical supervision, counseling, group meetings can be very beneficial.
I hope my info above helps in some way. I am sorry for your situation with your step daughter.