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Methadone assay

Product Method Size Catalog Price Quantity
Methadone assay Homogeneous Enzyme Immunoassay R1 2 x 16.9ml, R2 2 x 8ml DA4016 $647.20
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  • Format
    Liquid ready-to-use
  • Working Stability 2-8 °C
    Stable to expiry
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Intended Use

The Methadone assay is an in vitro diagnostic test for the qualitative and semi-quantitative detection of methadone in human urine on the RX daytona and the RX imola at the 300 ng/ml cut-off. The assay is calibrated against methadone.

This assay provides only a preliminary result. A more specific chemical method must be used in order to obtain a confirmed analytical result. Gas Chromatography/Mass Spectrometry (GC/MS) is the preferred confirmatory method. Clinical consideration and professional judgement should be exercised with any drug of abuse test result, particularly when a preliminary result is positive.

Clinical Significance

Methadone is a synthetic diphenylheptanonylamine opioid that has similar analgesic activity and potency as morphine when administered parenterally. However, unlike morphine, it reliably retains its effectiveness when given orally, and tolerance and physical dependency develop slowly. Although methadone is prescribed to relieve chronic pain, its primary medical application is the detoxification and/or maintenance treatment of narcotic or heroin addiction. The abuse potential of methadone is comparable to that of morphine due to its resembling pharmacological activity. Methadone is available in tablets and as a solution for parenteral injection. It is readily absorbed from the gastrointestinal tract when ingested, and metabolised extensively in the liver. Initial N-demethylation results in normethadone, which rapidly undergoes cyclization followed by dehydration to form the 2-ethylidene-1, 5-dimethyl-3, 3-diphenylpyrrolidine, commonly known as EDDP. Further N-demethylation yields a secondary metabolite, the 2-ethyl-5-methyl-3, 3-diphenyl-1-pyrroline (EMDP). The metabolites are secreted in urine or bile along with unchanged drug.


The assay is based on competition between drug in the sample and drug labelled with the enzyme glucose-6-phosphate dehydrogenase (G6PDH) for a fixed amount of antibody in the reagent. Enzyme activity decreases upon binding to the antibody, and the drug concentration in the sample is measured in terms of enzyme activity.

In the absence of drug in the sample, methadone-labelled G6PDH conjugate is bound to antibody, and the enzyme activity is inhibited. However, when free drug is present in the sample, antibody would bind to free drug; the unbound methadone-labelled G6PDH then exhibits its maximal enzyme activity.

Active enzyme converts nicotinamide adenine dinucleotide (NAD) to NADH, resulting in an absorbance change that can be measured spectrophotometrically at 340 nm.

Available Applications

RX series instruments, including:

RX daytona

RX imola