d-Methamphetamine and l-Methamphetamine
Drug Monitoring, Methamphetamine D/L Isomers, Urine - This test measures the ratio of the D and L isomers of methamphetamine in urine. Methamphetamine isomers are biomarkers to identify which forms of methamphetamine are present. The test is a definitive drug assay using the liquid chromatography/mass spectrometry (LC/MS-MS) method of analysis.
Quest Diagnostics Nichols Institute
Methamphetamine is a stimulant drug of abuse as well as a prescription drug used to treat attention deficit hyperactivity disorders (ADHD) and obesity. Methamphetamine has two isomer forms (D and L). The L isomer is used in over-the-counter nasal decongestant products and is also a metabolite of the drug selegiline. The D isomer is used for prescription methamphetamine and is also a metabolite of the drug benzphetamine. Illicit methamphetamine formulations are primarily the D form. Approximately 62% of an oral dose is excreted with ~33% as unchanged drug and ~66% metabolites (including amphetamine) .
According to the American Association for Clinical Chemistry (AACC), testing drugs/drug metabolites is recommended and effective for detecting the use of relevant over-the-counter, prescribed, and nonprescribed drugs, and illicit substances in pain-management patients . Laboratory testing is more effective than other physician tools for the detection of these substances in pain-management patients and is useful for routine monitoring of adherence. Instances where unchanged drug is detected, but metabolite(s) is not, may be indicative of drug added to the specimen after collection (eg, pill shaving, drug spiking) .
Note: No single monitoring approach provides adequate information about the pattern or dose of patient drug use. Safest prescribing habits should include a combination of tools and laboratory test results to correctly detect drug use patterns.
Urine drug test results equal to or greater than cutoff are reported as quantitative values and results less than cutoff are reported as negative. Quantitative values cannot be used to assess the drug dose because the drug is extensively metabolized and excreted in the urine.