What and how much were you using before you started taking methadone? That is what should determine the intensity and duration of your withdrawals rather than 1 week of methadone. Chances are you will have to endure the withdrawal process but, if you're lucky, you should only withdraw from the drug you were taking prior to the methadone.
All the best. Regards Jeremy. Recovered Ex-Addict
I wouldn't expect much of anything but it is good that you have only been on for a week.You may have some very mild symptoms.