Methadone is a central nervous system (CNS) depressant. Methadone is used as an analgesic. It is administered either orally, subcutaneously, intravenously or by intramuscular injection. The use of methadone may result in adverse effects such as nausea, headache, vomiting, impotence, cardiac arrhythmia and hallucinations. It also produces marked sedative effect with repeated administration as a result of drug accumulation. The duration of effect of methadone is 12-24 hours. Its major urinary excretion products are methadone, EDDP (2-ethyldiene-1,5-dimethyl-3,3-diphenylpyrrolidine) and EMPD (2-ethyl-5-methyl-3,3 - diphenyl-pyrroline). The percentage of methadone excreted unchanged in urine is 5-50% much higher than EDDP and EMPD, of the dose in 24 hours. The half-life of methadone is 15 to 60 hours. This test one step test for methadone detects the presence of methadone in human urine specimens, qualitatively.