RESUMO
In urine drug testing, enantiomer analysis is used to determine whether a positive methamphetamine result could be due to use of an over-the-counter (OTC) nasal inhaler containing L-methamphetamine. D-methamphetamine at more than 20% of the total is considered indicative of a source other than an OTC product. This interpretation is based on a 1991 Department of Health and Human Services (HHS) Technical Advisory. We performed studies to verify the methamphetamine enantiomer content of current OTC nasal inhalers and to evaluate current laboratory testing capabilities. This study demonstrated that OTC inhalers contain less than 1% D-methamphetamine. A proficiency testing (PT) set for HHS-certified laboratories performing methamphetamine enantiomer testing found D-methamphetamine percentages that were consistently 1 to 3% higher than theoretical due to optical impurity of the derivatizing reagent N-trifluoroacetyl-L-prolyl chloride (L-TPC). The PT results also demonstrate that laboratories can accurately determine 20% D-methamphetamine in samples with total methamphetamine concentrations down to 250 ng/mL. Based on these studies, the guideline of >20% D-methamphetamine is appropriate for interpreting results obtained using current laboratory methods.
Assuntos
Estimulantes do Sistema Nervoso Central/urina , Guias como Assunto , Metanfetamina/urina , Detecção do Abuso de Substâncias , Administração por Inalação , Estimulantes do Sistema Nervoso Central/administração & dosagem , Estimulantes do Sistema Nervoso Central/química , Estimulantes do Sistema Nervoso Central/farmacocinética , Contaminação de Medicamentos , Controle de Medicamentos e Entorpecentes/métodos , Humanos , Imunoensaio , Indicadores e Reagentes/química , Ensaio de Proficiência Laboratorial , Limite de Detecção , Metanfetamina/administração & dosagem , Metanfetamina/química , Metanfetamina/farmacocinética , Descongestionantes Nasais/administração & dosagem , Descongestionantes Nasais/química , Descongestionantes Nasais/farmacocinética , Descongestionantes Nasais/urina , Medicamentos sem Prescrição/administração & dosagem , Medicamentos sem Prescrição/análise , Medicamentos sem Prescrição/química , Medicamentos sem Prescrição/farmacocinética , Prolina/análogos & derivados , Prolina/química , Estereoisomerismo , Detecção do Abuso de Substâncias/normas , Estados Unidos , United States Dept. of Health and Human Services , United States Substance Abuse and Mental Health Services AdministrationRESUMO
BACKGROUND: A proficiency testing scheme was set up for the DRUID (Driving under the influence of Drugs, Alcohol and Medicines) research project, funded by the European Commission, in which oral fluid is analysed by eleven laboratories. A common collection and analysis methodology is used: Statsure Saliva Sampler is used for collection and LC-MS/MS or GC-MS confirmation analysis of 22 substances is performed on all samples. Despite internal validation and quality control samples, external quality assessment is still necessary to further increase comparability of results. Four rounds of proficiency testing (PT) were organized between March 2008 and September 2009. METHODS: Qualitative results were evaluated using sensitivity and specificity. Quantitative results were evaluated using z-scores and the standard deviation of Horwitz. RESULTS: Specificity was above 99% in each round, sensitivity per analyte varied between 81.7 and 100%, and 20 out of 22 analytes had a sensitivity above 90%. The percentage of satisfactory z-scores increased from 79.4% to 89.2%. This trend was seen for all drug classes, except zopiclone. Results were discussed with participating laboratories and problems were addressed. CONCLUSIONS: Because of these corrective actions, DRUID laboratories have a lower variation in results than previously published PT schemes in oral fluid.