EDDP—also known as 2-Ethylidene-1, 5-Dimethyl-3, 3-Diphenylpyrrolidine—is the chief metabolite of Methadone, produced when the human body modifies Methadone in order to eliminate it. Methadone levels in urine vary widely depending on factors such as drug dose, user metabolism, and urine pH. EDDP levels are pH-resistant and are therefore the preferred method for assessing compliance with drug abuse therapy, the most common reason for EDDP testing.

Some Heroin users who attend Methadone treatment centres sell their prescribed Methadone illegally while continuing to abuse Heroin. While providing a urine sample for progress testing, these users will “spike” their urine by adding Methadone to it in order to trigger a positive result for Methadone.

Testing for EDDP as well as Methadone provides a clearer picture of drug use. Users who sell their Methadone while continuing their Heroin use will test negative for EDDP, since their bodies did not produce this metabolite while processing the Methadone. Patients known as “fast metabolizers” whose bodies process Methadone very quickly compared to its metabolite EDDP may test negative for Methadone, but their EDDP levels will confirm their compliance to the narcotic maintenance treatment program.

EDDP can be detected within four to six hours after use and can be cleared by the body within two to three days after consumption. EDDP has a cut-off level of 100 ng/ml and a detection window of up to seven days.