I've been on methadone quite a long time and finally ramping off it.
First, don't let yourself get on a high dose and if you do start reducing it as much as possible within reason. Even 15 mgs a day can really back you up. I didn't stop getting backed up until I was under 10 mgs a day. I'm at 6 now..and don't let anyone tell you that you can't drop your dosage..If need be find a different clinic. I was able to drop 5 mgs a week until I was down to 10mgs a day then started dropping 1mg every 2 weeks..results with this will vary depending on you.. I've weened completely off it before so it can be done. It just takes time. At one time I was on over 150 mgs every day..
Second, LOTS OF fresh fruits and prune juice every day. In off seasons like winter use canned fruit, but keep the fruit going in. Some fruits work better than others so you'll have to experiment with different types. Prunes and plumbs generally do better..Watermelon is good too. By any definition I am a fruitarian.. For better or worse..
AVOID ALL CHEESE, dairy products and especially white bread and pasta..If you must eat them do it in extreme moderation. It limits what you may be used to eating, but better to limit your diet than have to suffer an all day grunting session on a toilet. It can get even worse till your forced to reach up inside yourself to break up your own turds..I've been there several times.
WATER! Drink lots of water even if you don't feel like it..and avoid high sugar drinks..Nothing helps you stay constipated like dry turds..
I hope some of these suggestions help. I've fought this for years now.. Good luck.
If you feel like discussing different strategies feel free to contact me at amello.m.59@ the g mail address..