¹²⁵I Radioimmunoassay for the Dual Detection of Amphetamine and Methamphetamine
Ward, C
Research Scientist, Research Group Leader, and Director, respectively, Department of Toxicology International Drug Monitoring Business Unit, Roche Diagnostic Systems, Inc., Branchburg, NJ.

McNally, AJ
Research Scientist, Research Group Leader, and Director, respectively, Department of Toxicology International Drug Monitoring Business Unit, Roche Diagnostic Systems, Inc., Branchburg, NJ.

Rusyniak, D
Medical Student, Bowman Gray School of Medicine, Winston-Salem, NC.

Salamone, SJ
Research Scientist, Research Group Leader, and Director, respectively, Department of Toxicology International Drug Monitoring Business Unit, Roche Diagnostic Systems, Inc., Branchburg, NJ.


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) drugs and this cross-reactivity was further reduced by the addition of sodium periodate into the reaction mixture to oxidize the b-hydroxylamines. The double (second) antibody assay uses ¹²⁵I-radiolabeled derivatives of both D-amphetamine and D-methamphetamlne 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 drug 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.

Keywords:
amphetamine, amphetamines, detection of drugs, drug identification, forensic science, radioimmunoassay, RIA, toxicology

Paper ID: JFS396941486

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Author Ward C, McNally AJ, Rusyniak D, Salamone SJ Title ¹²⁵I Radioimmunoassay for the Dual Detection of Amphetamine and Methamphetamine Symposium , Committee on