Positive methadone plasma/serum test 2018-09-11T23:47:39Z Methadone is an opioid drug that is used to treat severe pain or in the treatment of individiuals with opioid dependency. Detection of methadone or its metabolite 2-ethylidene-1,5-dimethyl-3,3- diphenylpyrrolidine (EDDP) in plasma or serum. Plasma/serum xenobiotic