Interpretation of methamphetamine and amphetamine enantiomer data

Interpretation of drug testing results is a challenging and complex task, particularly when the interpretation can result in establishing legitimate use of a drug or illicit use with all of its attendant complications (i.e., loss of job, criminal prosecution, etc.). One of the more challenging drugs to interpret is methamphetamine. While methamphetamine is a schedule II controlled substance, the l-enantiomer of methamphetamine is found in the Vick's Inhaler, which is a product exempted from control. For this reason, while identification of methamphetamine and amphetamine in the urine of an individual can clearly establish the use of methamphetamine, it does not prove the use of a controlled substance. Use of racemic methamphetamine can make the interpretation even more difficult because of the different metabolism and excretion of l- and d-methamphetamine. Enantiomeric characterization of methamphetamine may not give unequivocal results. Evaluation of experimentally derived and published data from urine samples containing l- and d,l-methamphetamine indicates that use of the enantiomeric distribution of amphetamine affords unambiguous interpretation. Because the l-enantiomer is the only possible finding in an individual who is using the Vick's Inhaler, detection of the d-enantiomer or a mixture of the d- and l-enantiomers clearly establishes the use of a controlled substance. Without a prescription from appropriate medical personnel, this detection would indicate the illicit use of a controlled substance.