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

Abstract

AbstractBackground: 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.