EDDP (2-ethylidene-1, 5-dimethyl-3, 3-diphenylpyrrolidine) is the metabolite of methadone, and testing for EDDP is used to determine the effective intake of Methadone when it is used as patient substitution treatment during use cessation. Methadone metabolizes in the liver into EDDP and EMDP. However, the rates of metabolism vary between individuals. The detection of EDDP in place of Methadone avoids the problems related to the metabolic differences of each person.