by Cody JT, Valtier S, Nelson SL.
Academy of Health Sciences, MCCS-HMP PA Branch, Fort Sam Houston, Texas 78234-6138, USA.
J Anal Toxicol. 2003 Oct; 27(7): 485-92
ABSTRACT
Amphetamine remains a widely abused drug throughout the world. It is also used therapeutically for weight loss, narcolepsy, and attention deficit disorder with hyperactivity (ADHD). ADHD has grown dramatically recently both in terms of diagnosis and treatment. Increasingly, older individuals are diagnosed and treated for ADHD, and treatment often continues into adulthood. Of the available treatments for ADHD, Adderall is widely prescribed. Despite its widespread use, there are no published data regarding the expected amphetamine excretion profile following its use. This is problematic because, in this case, medical review officers (MRO) and forensic toxicologists are asked to assess results in terms of use pursuant to valid medical prescription without specific data on which to base a sound decision. To address this situation, a study to determine the concentration and enantiomer composition of amphetamine excretion following administration of Adderall was undertaken. Adderall (20 mg) was administered to five healthy subjects with all subsequent ad lib urine samples (total urine void) collected for seven days. Adderall is a 3:1 mixture of d- and l-enantiomers of amphetamine salts. Peak amphetamine concentrations ranged from 2645 to 5948 ng/mL. Samples containing > or = 500 ng/mL of amphetamine (the administrative cutoff for a positive result by gas chromatography-mass spectrometry) were seen up to 47:30 h post dose. The number of samples that contained amphetamine concentrations of > or = 500 ng/mL ranged among individuals from 7 to 13. As anticipated, analysis showed the d-enantiomer to be in excess of the l-enantiomer, with the proportion of l-enantiomer increasing over time. Because of the mixture of enantiomers, not all samples that contained > or = 500 ng/mL of amphetamine were positive when tested by immunoassay. The drug concentration profiles were quite variable within and between subjects because of dilution and fluctuations in pH of the samples. These results are the first to describe the excretion of amphetamine following administration of Adderall. The presence of the l-enantiomer separates this drug from other preparations of the drug that are composed of only the d-enantiomer (i.e., dexedrine and much illicit amphetamine), thus readily differentiating them from Adderall use. Some illicit and medicinal amphetamine is, however, a mixture of amphetamine enantiomers. Because the enantiomers are metabolized at different rates, their proportion offers the opportunity to describe excretion versus time. Coupling this data with drug concentration makes it possible for forensic toxicologists and MROs to come to an informed decision about the involvement of this drug in a positive drug test result. Using the combination of enantiomer composition and quantitative data will allow MROs and forensic toxicologists to better assess the use of this drug from abuse of amphetamine.
