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BACKGROUNDConfirmation of a workplace drug test requires urinary methamphetamine (MAMP) and amphetamine (AMP) concentrations > or = 500 and 200 micro g/L, respectively, but cutoffs at half those values (250/100 micro g/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.METHODSVolunteers (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.RESULTSMAMP 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 micro g/L, respectively. Peak MAMP concentrations (1871-6004 micro g/L) after single doses occurred within 1.5-60 h. MAMP > or = 500 micro g/L was first detected in the first or second void (1-11 h) at 524-1871 micro g/L. Lowering the MAMP cutoff to 250 micro g/L changed the initial detection time little. AMP > or = 200 micro g/L was first detected in the 2nd-13th (7-20 h) post-administration voids. At a cutoff of 100 micro g/L, AMP was first confirmed in the second to eighth void (4-13 h). Reducing the cutoff to 250/100 micro g/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%.CONCLUSIONSAt 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.

Duration of Detectable Methamphetamine and Amphetamine Excretion in Urine after Controlled Oral Administration of Methamphetamine to Humans