Hi cococoffee,
I got a kick out of your name. I had a friend, many years ago, whom I nicknamed CoocooCokeoo. He used to call me Zoomzoom, and I called him Cocoocokecoo.
Anyway, on to your question. There's no reason a Benzo can't be taken with Mdone so long as the person isn't allergic to neither drug. But it has to be done with caution because both drugs are depressants and a person can die from mixing too much. Therefore only a doc should mix them. So mixing them would cause him to be more tired, even if he is mixing them safely. They would still cause additional tiredness. However, the muscle twitches in his arms and legs are signs of wds from Opiates. How long is he on Mdone Maintenance, and what was he on before that? What and how much of it? My guess is he's not yet on enough Mdone. Most clinics start you at a low dose and then go up as needed. I understand this process can take several weeks. However, eventually the correct dose for each person is usually found. But if he's mixing a Benzo with the Mdone because the dose is too low, and they find out, he will be kicked out of the program. Even if they don't find out, by mixing a Benzo with the Mdone they will never find the correct dose. Listen to me, Mdone can be a life saving drug, like Subox can too. But a person has to be honest about it. We have several people, who came here from time to time, that will swear to you Mdone saved them from a life of Heroin abuse. And they are quite right. It did. But finding the proper dose can be a long difficult process, for some people. For others it can be found after 1 or 2 dose adjustments. It's very important that the clinic know every psychoactive drug your bf takes. Even ad meds like Pristiq, Cymbalta, Prozac, etc.
So my guess is that due to a low dose of Mdone, he's having wds (leg and arm twitches) and so he's attempting to make the wds go away with a Benzo. That won't work. He needs to tell them he's still having wds and they need to raise his Mdone dose.
I hope this helped.