Antecedents:

Drugs consumption constitutes a problem in the military media, being cannabis and cocaine the illegal drugs with a highest prevalence of consumption. Laboratories situated in pharmaceutical establishments are responsible for carrying out the preliminary analysis of screening samples, as it’s shown the I.T. 1/2012 of IGESAN, being confirmed the positive results of the sein the Toxicology Institute of Defense. Samples whose results are positives to abused drugs would be kept for six months at -20 °C, if required by repeating the test. Metabolites are present in urine could be deteriorated during storage and conservation, getting different results if we go over the sample. This is important for laboratories to know the stability of the metabolites present in the samples.

Objective:

to investigate cannabis and cocaine metabolite’s stabilities in urine, after have been kept in -20 °C during more than a year.

Material and methods:

91 urine samples turned out positives (65 to cannabis, 25 to cocaine and 1 to both), using the analyzer Cobas Integra 400 plus® (semiquantitative-qualitative method using a nimmunological technique, with cut off so 50 ng/ml for cannabis and 300 ng/ml for cocaine). They were stored in plastic tubes at -20 °C during more than a year. After to defrost and shaking soft lytohomogenize, they were reanalyze with the same analyzer.

Results:

for the 66 positive samples of cannabis metabolites it produced a mean decrease from initial values of -22.89% (range -73.36% to +43.15%). For the 26 positive samples of cocaine metabolites it produced a mean decrease from initial values of -4.02% (range -49.01% to +7.03%).

Conclusions:

we could notice that cannabis metabolites present in the more than a year frozen urines, decrease in a greater extent than those of cocaine. Cannabis percentages were similar to those obtained by other authors, although not in cocaine metabolites case.