Did the doctor give you instructions on how to take this?
Are you under a Drs care for Methadone? Are you going to get the Subs under a Drs maintenance program? Subs are nothing to mess around with and just go from Dones to Subs. Methadone is a full opiate blocker & Subs partial opiate blocker, but both have there w/ds and they are both very synthetic and hard to w/ds from. You would be better to just taper the Dones and get into some kind of aftercare. Addiction goes way beyond after the removal of these stims. It will take a great Support system to stay clean.
PS. I do have a book that tells me how long it takes to do the switch.
Talk with a DR for sure!!!
Call a pharmacist. He will give you the best answer