title: Methadone radioimmunoassay: two simple methods.
abstract: Two simple and economical radioimmunoassays for methadone in blood or urine are described. Haemolysis, decomposition, common anticoagulants and sodium fluoride do not affect the results. One assay uses commercially-available [1-3H](-)-methadone hydrobromide as the label, while the other uses a radioiodinated conjugate of 4-dimethylamino-2,2-diphenylpentanoic acid and L-tyrosine methyl ester. A commercially-available antiserum is used in both assays. Normethadone and alpha-methadol cross-react to a small extent with the antiserum while methadone metabolites, dextropropoxyphene, dipipanone and phenadoxone have negligible cross-reactivities. The 'cut-offs' of the two assays as described are 30 and 33 ng ml-1 for blood, and 24 and 21 ng ml-1 for urine. The assay using the radioiodinated conjugate can be made more sensitive if required by increasing the specific activity of the label.
mesh_terms: D002851:Chromatography, High Pressure Liquid; D006801:Humans; D007106:Immune Sera; D008691:Methadone / Q000032:analysis* / Q000097:blood / Q000652:urine; D011863:Radioimmunoassay
chemical_list: D007106:Immune Sera; D008691:Methadone