I was a little confused after reading your post.....only because I needed more information. What kind of "rehab" unit or facility are we talking about? What is "mssr?" I'm an old War Horse in the profession, so don't be too "amazed" at my questions.
Just curious.....what happened to the "old" doc? And how long has the "new" doc been on the scene?
I'll take a stab at answering your post based on the possibility that you are talking about a post-op ortho kind of rehab unit..........
My experience tells me that such patients, depending on the kind of surgery i.e., hip vs. knee, etc. and their general overall conditon requires I.M. narcotic pain relief for the first 24-48 hours (possibly longer, depending on the surgery and patient) - but usually no longer than that. After that, pain relief is pretty well accomplished with some kind of p.o. analgesic such as Vicodin, Percocet, Percodan, Tylenol with Codeine, etc. Correct me if I'm wrong (anybody with more experience than I)......but what seems "peculiar" is using Methadone for pain relief for this kind of setting. I've used it in Oncology many times, for a variety of reasons, but never in an Ortho setting.
I also thought, as I read your post, how we as Nurses have a tendency to be "speculative" about new members of the staff, be it Nurses, Doctors, or otherwise, until we see the "newbies" in action for a period of time. It sounds like you liked the "old" doc and were used to his/her way of doing things.
Suggestion: Take your genuine concerns to your Unit Manager, or whoever is in Charge and hash things over a bit.