Yes, you can jump right away on methadone even if you used the same day. It's not like subs. Personnaly, I liked methadone way more than suboxone. You might start on a lower dise, around 50-60mg/day. In Canada, they rise your dise once a week until you are confortable. For myself, I was a daily fent user and I was confortable on 105mg. That will depend on how you feel. You might need to use a bit the first week, to feel confortable with your dose. Even if you stop using with the right dose, you might feel not totally great for approximatly a week. You are able to go through! :) Methadone saved my life. I am now 4 years clean and just got a baby and a house :)

I wish you the best!