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1 Chemistry and Drug Metabolism Section, Intramural Research Program, National Institute on Drug Abuse, 5500 Nathan Shock Dr., Baltimore, MD 21224.
2 ConeChem Research, LLC, 441 Fairtree Dr., Severna Park, MD 21146.
3 Amgen Inc., One Amgen Center Dr., Thousand Oaks, CA 91320.
aAuthor for correspondence. Fax 410-550-2971; e-mail joyler{at}intra.nida.nih.gov.
Background: Confirmation of a workplace drug test requires urinary methamphetamine (MAMP) and amphetamine (AMP) concentrations 
500 and 200 µg/L, respectively, but cutoffs at half those values (250/100 µg/L) have been proposed. We determined the urinary excretion of MAMP after oral ingestion and examined the effect of using lower cutoffs on detection of exposure.
Methods: Volunteers (n = 8) ingested four 10-mg doses of MAMP · HCl daily over 7 days, and five of them ingested four 20-mg doses 4 weeks later. After ingestion, the volunteers collected all urine specimens for 2 weeks. After solid-phase extraction, MAMP and AMP were measured by gas chromatography–positive chemical ionization mass spectrometry with dual silyl derivatization.
Results: MAMP and AMP were generally detected in the first or second void (0.7–11.3 h) collected after drug administration, with concentrations of 82–1827 and 12–180 µg/L, respectively. Peak MAMP concentrations (1871–6004 µg/L) after single doses occurred within 1.5–60 h. MAMP 500 µg/L was first detected in the first or second void (1–11 h) at 524-1871 µg/L. Lowering the MAMP cutoff to 250 µg/L changed the initial detection time little. AMP 200 µg/L was first detected in the 2nd–13th (7–20 h) post-administration voids. At a cutoff of 100 µg/L, AMP was first confirmed in the second to eighth void (4–13 h). Reducing the cutoff to 250/100 µg/L extended terminal MAMP detection by up to 24 h, increased total detection time by up to 34 h, and increased the total number of positive specimens by 48%.
Conclusions: At the lower cutoff, initial detection times are earlier, detection windows are longer, and confirmation rates are increased. Elimination of the AMP requirement would increase detection rates and allow earlier detection.
The following articles in journals at HighWire Press have cited this article:
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  A. J. Barnes, M. L. Smith, S. L. Kacinko, E. W. Schwilke, E. J. Cone, E. T. Moolchan, and M. A. Huestis Excretion of Methamphetamine and Amphetamine in Human Sweat Following Controlled Oral Methamphetamine Administration Clin. Chem., January 1, 2008; 54(1): 172 - 180. [Abstract] [Full Text] [PDF]
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 A W Jones and L Karlsson Relation between bloodand urine-amphetamine concentrations in impaired drivers as influenced by urinary pH and creatinine Human and Experimental Toxicology, December 1, 2005; 24(12): 615 - 622. [Abstract] [PDF]
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I. Kim, A. J. Barnes, R. Schepers, E. T. Moolchan, L. Wilson, G. Cooper, C. Reid, C. Hand, and M. A. Huestis Sensitivity and Specificity of the Cozart Microplate EIA Cocaine Oral Fluid at Proposed Screening and Confirmation Cutoffs Clin. Chem., September 1, 2003; 49(9): 1498 - 1503. [Abstract] [Full Text] [PDF]
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R. J.F. Schepers, J. M. Oyler, R. E. Joseph Jr, E. J. Cone, E. T. Moolchan, and M. A. Huestis Methamphetamine and Amphetamine Pharmacokinetics in Oral Fluid and Plasma after Controlled Oral Methamphetamine Administration to Human Volunteers Clin. Chem., January 1, 2003; 49(1): 121 - 132. [Abstract] [Full Text] [PDF]
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