hiya, im a pharmacist (hmmm saying that a lot today) and i would strongly suggest that he finishes his methadone treatment before doing anything with roids.
firstly methadone treatment doesnt take that long (weeks really) and secondly, some Anabolic Androgenic Steroids (AAS) result in mood changes which may affect his control over his desire to seek more painkillers (depends how bad this addiction was)
of course some Anabolic Androgenic Steroids (AAS) may blunt his need for painkillers because of the euphoria some induce, but its not a risk youd take in the middle of methadone treatment
just tell him to stay put until he is done.
besides, gathering all the drugs needed for a decent cycle (ancilliaries etc) and getting yourself prepped and in the right frame of mind take a bit of time. use it.
the guy we are talking about is in a country where steroids are allowed, right? if not, then disregard the entire post, roids are illegal without a script.