English 
Italian CONTRIBUTI SCIENTIFICI – Scientific Papers
Volume:
Biochimica Clinica 2014; 38(2) 103-109
Pubblicato on-line:
DOI:
Stabilità delle principali droghe d’abuso in campioni di urine non trattate rispetto a campioni di urine stabilizzate
AUTORI
1Centro di riferimento regionale per il dosaggio dei farmaci e delle sostanze d’abuso nei liquidi biologici, Struttura Organizzativa Dipartimentale Laboratorio Generale e 2Centro di riferimento regionale per il controllo di qualità, Struttura Organizzativa Dipartimentale Sicurezza e Qualità in Laboratorio, Azienda Ospedaliero-Universitaria di Careggi, Firenze
ABSTRACT
Drug of abuse stability in native urine specimens vs. stabilized urine samples
Effective urine drug of abuse testing requires an understanding of the stability of drugs and their metabolites excreted in the urine matrix. As timing of specimen collection is crucial in urine screening of drugs, potential degradation that may occur between, e.g., the initial test and the re-test of samples, should be considered. Stability characteristics depend on the drug, specimen’s pH, storage temperature, light exposure, bacteria contamination and material of the urine container. The purpose of this study was to determine the stability in urine specimens of four classes of drugs and their metabolites (cannabinoids, opiates, cocaine and methadone) for a maximum of 20 weeks. In the study design, a freshly authentic pooled urine specimen was aliquoted into vials (plastic and glass) and these were stored at freezing (-20 °C), at fridge (4 °C) and at room temperatures and reanalyzed every one/two weeks up to 20 weeks. In parallel, we extended the study analysing one urine pool stabilized using various techniques of thawing and filtration for preventing the decomposition of drugs of abuse. In the native specimens, analytes were relatively stable when stored for extended periods of time at -20 °C. Concentrations of cannabinoids, cocaine metabolites and morphine in not-pretreated samples decreased over time at 4 °C and at room temperature. Methadone did not show relevant loss of drug concentrations during fridge storage. Manufactured urine pool was stable, showing little changes between day 1 and after 10 weeks at 4 °C. Morphine, cannabinoids and methadone showed no loss in drug concentrations after two weeks at room temperature, while benzoylecgonine concentrations significantly decreased after one week.