This is an excerpt from a memorandum I drafted. I believe it contains very basic yet important information for any attorney who is dealing with a matter in which drug testing is performed and is not familiar with drug testing principals and processes. I am working on expanding on the initial work and will add information as necessary. If anyone has comments, suggestions or recommendations please feel free to contact me.
Metabolite Testing for Cocaine
Metabolism is defined as the sum of the physical and chemical processes in an organism by which its material substance is produced, maintained, and destroyed, and by which energy is made available[1]. Thus metabolism occurs whenever any substance is taken into the body and any substance that is not used is excreted. Part of metabolic process is to break down substances. Recreational drugs are subject to this metabolic process as well and may be excreted in complete form or in reduced forms known as metabolites. Cocaine is almost completely metabolized, meaning very little cocaine (about 1%) will be excreted as waste[2]. This metabolism of cocaine occurs in the liver. Most cocaine is excreted as benzoylecgonine. Other lesser metabolites of cocaine are ecgonin, methylester, and ecgonine. Cocaine and its metabolites may be quantitated in blood, plasma, or urine. Benzoylecgonine is detectable in urine within a few of hours after cocaine inhalation and remain detectable in concentrations higher than 1000 ng/mL for as long as 48 hours[3].
Most cocaine immunoassay-screening test cross-react with the major cocaine metabolites, but chromatographic techniques can easily distinguish and separately measure each metabolite. Cautious interpretation of test results may allow distinction between a passive or active user and between smoking or other routes of administration[4]. Screening assays may not distinguish between the different metabolites and usually will not quantitate the amount of metabolite present where as Gas chromatography- mass spectrometry (GC/MS) test can and are also capable of quantitation of the metabolites.
Gas chromatography–mass spectrometry is a method that combines the features of gas-liquid chromatography and mass spectrometry to identify different substances within a test sample[5]. Applications of GC-MS is broad ranging from drug detection to identification of unknown samples. GC-MS has been widely heralded as the "gold standard" for forensic substance identification because it is used to perform a specific test by positively identifying the actual presence of a particular substance[6]. The GC-MS test essentially is finding the “fingerprint” of the chemical and is also capable of detecting minute amounts of cocaine secreteted by the body[7]. The GC-MS test is used to confirm results of immunoassay screening test for cocaine[8]. GC-MS test stands up in court by developing chain of custody by quantitation[9].
[1] See Dictionary.com definition of Metabolism. http://dictionary.reference.com/browse/metabolism
[2] Beckham Coulter, Inc 2010 Procedure: Cocaine Metabolites OSR9H229.
[3] Beckham Coulter, Emit II Plus Cocaine Metabolite Assay 9H052.5D_B.
[4] R. Baselt, Disposition of Toxic Drugs and Chemicals in Man, 9th edition, Biomedical Publications, Seal Beach, CA, 2011, pp. 390–394.
[5] http://en.wikipedia.org/wiki/Gas_chromatography%E2%80%93mass_spectrometry
[6] Id, footnote 4.
[7] Per interview with Eric Vas Binder at University of Michigan Pathology laboratory.
[8] Id.
[9] Id.