125I radioimmunoassay for the dual detection of amphetamine and methamphetamine

C. Ward, A. J. McNally, D. Rusyniak, S. J. Salamone

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9 Scopus citations

Abstract

A radioimmunoassay that exhibits a nearly equivalent response to D- amphetamine and D-methamphetamine in urine over the assay range of 0 to 1000 ng/mL while displaying low cross-reactivity to L-amphetamine and L- methamphetamine (4.6% and 2.4%, respectively) has been developed. In addition, methylenedioxy-amphetamine (MDA) and methylenedioxymethamphetamine (MDMA) were detectable in the assay with cross-reactivity levels of >100% and 77% respectively. Little cross-reactivity was observed with the commonly encountered over-the-counter (OTC) drags and this cross-reactivity was further reduced by the addition of sodium periodate into the reaction mixture to oxidize the β-hydroxylamines. The double (second) antibody assay uses 125I-radiolabeled derivatives of both D-amphetamine and D-methamphetamine as tracers in combination with two highly specific sheep antisera directed against D-amphetamine and D-methamphetamine. The assay exhibits a dose response of approximately 90,000 dpm from 0 to 1000 ng/mL of D-amphetamine or D-methamphetamine with a minimum detectable dose for either drag of approximately 25 ng/mL. With a cut-off level of 500 ng/mL, the assay gave a positive result for 100% of the 111 clinical samples containing GC/MS confirmed (at or above the NIDA GC/MS cut-off values) levels of amphetamine and/or methamphetamine. Eighty eight samples that screened negative in a clinical laboratory were all negative in the assay. Nineteen samples which were incorrectly identified as positive by other commercially available amphetamine assays were negative in this RIA.

Original languageEnglish (US)
Pages (from-to)1486-1496
Number of pages11
JournalJournal of Forensic Sciences
Volume39
Issue number6
StatePublished - Dec 1 1994

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Keywords

  • RIA
  • amphetamines
  • detection of drugs
  • toxicology

ASJC Scopus subject areas

  • Pathology and Forensic Medicine
  • Genetics

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