EDDP is the most important metabolite of methadone. It is excreted in the bile and urine together with the other metabolite EMPD. EDDP is formed by N-demthylation and cyclisation of methadone in the liver.
Therefore, detection of the metabolite EDDP instead of methadone itself is useful because interferences of the patient’s metabolism are avoided. EDDP can be detected within 4 to 6 hours after use. It can be cleared by the body within 2 to 3 days after use.