Published: Journal of Analytical Toxicology, Volume
23,
Number 6,
October 1999,
pp.511-517
Metabolic Production of Amphetamine Following Multidose Administration of
Clobenzorex*
Kerri L. Baden, Sandra Valtier and John T. Cody
The interpretation of urine drug-testing results can have important forensic and
legal implications. In particular, drugs that are metabolized to amphetamine or
methamphetamine or both pose significant concerns. In this study, clobenzorex,
an anorectic drug that is metabolized to d-amphetamine, was administered to five
subjects. Each subject took 30 mg daily for seven days, and individual urine samples
were collected ad lib for 14 days beginning on the first day the drug was administered.
Urine pH, specific gravity, and creatinine values were determined for each sample.
Gas chromatography–mass spectrometry (GC–MS) was used to determine the
excretion profile of amphetamine and clobenzorex using a standard procedure for
amphetamines with additional monitoring of ions at m/z 118, 125, and 364 for the
detection of clobenzorex. Peak concentrations of amphetamine were found at 82
to 168 h after the first dose and ranged from approximately 2900 to 4700 ng/mL
amphetamine. The use of a regioisomer (3-Cl-benzylamphetamine) as internal standard
allowed for accurate quantitation of the parent drug. Peak concentrations of clobenzorex
were found at 50 to 120 h after the first dose and ranged from approximately 8
to 47 ng/mL clobenzorex. However, in many samples, clobenzorex was not detected
at all. This analysis revealed that the metabolite, (amphetamine) is present in
much higher concentrations than the parent compound, clobenzorex. Yet even at
peak amphetamine concentrations, the parent was not always detected (limit of
detection 1 ng/mL). Thus, in the interpretation of amphetamine-positive drug-testing
results, the absence of clobenzorex in the urine sample does not exclude the possibility
of its use.
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