Methadone urine drug test is a one step rapid immunoassay designed to detect methadone in human urine at a cut-off concentration of 300 ng/ml. Methadone is a synthetic opioid and used for the treatment of severe pain. Methadone generally remains detectable in human urine for up to 14 days after usage. Methadone urine tests are available in cassette and dip stick formats.