Detection of amphetamine following administration of fenproporex

Drugs that are metabolized to amphetamine or methamphetamine are potentially significant concerns in the interpretation of amphetamine-positive drug testing results. A number of different compounds have been reported to produce amphetamine in the urine of users. One of these compounds, fenproporex, has been shown to produce amphetamine. Previous reports indicate that the parent compound can be detected only for a few hours following administration, whereas the amphetamine can be detected for several days. Administration of fenproporex to five healthy volunteers resulted in amphetamine being detected in the urine of all subjects. Peak concentrations of amphetamine were detected at approximately 6-20 h postdose and ranged from approximately 1200 to 2100 ng/mL amphetamine. Amphetamine could be detected (> 5 ng/mL) in the urine for up to 119 h. Analysis of the metabolically produced amphetamine showed the presence of both enantiomers, which can be helpful in the differentiation of some illicit amphetamine use from the use of this precursor drug. More significantly, all samples that contained amphetamine at a concentration of at least 500 ng/mL were shown to also contain measurable amounts of the parent compound.