How do you detox off high dose of methadone at home with stuff you can buy over-the-counter at stores?

You Don't: You don't. This is an insanity to think one can detox on their own off of methadone. This is setting you up to fail before you even start. Please get to a medical detox unit where this can be done with prescription medications and under direct medical supervision.

DETOX: Typical detox from Methadone is done under supervision by decreasing less than 10% at day for a typical 21 day taper. This should be managed with a pain medicine specialist or addiction specialist.