What you need to do is to slowly ween yourself down from the Methadone in 10 milligram increments. The slower the better. Take your time and keep steadily reducing the dose. If you can get it down to about 30 milligrams per day or less then you should try to finish your detox in a drug rehab center. There they can give you other medication that will help you to be fully detoxed from the drug and become entirely drug free.
Many people who were on Methadone as a maintenance drug are switching over to Suboxone because it does not really get you high and give you the same doping effect that Methadone does. If you are hooked on Methadone and you still feel that you need something long term for either pain or for opiate dependence then you should look into the possibility of switching over to Suboxone. Talk to your doctor about it and look into the cost of doing so. Unfortunately it is usually more expensive to do so but it is a much better option in terms of the side effects and the dependency issue.
Learn more about Methadone addiction and a drug detox program.