Hi there ~
I understand your concerns. Having side effects when you are detoxing from a medication such a methadone
is common. Consulting a local doctor for symptomatic treatment is usually all that is needed to treat your condition. The feeling of cramping may be treated with NSAIDs or non steroidal anti inflammatory drugs and / or muscle relaxants either centrally or peripherally acting ones. Please visit with and consult a local doctor for the appropriate prescriptions.
I hope this helps. Take care and have a lovely day!