Development of a method for the quantitation of benzphetamine metabolites in human urine by high-performance liquid chromatography.

We developed a high-performance liquid chromatography (HPLC) method for quantitating p-hydroxy-N-benzylamphetamine glucuronide (pHBAG) and p-hydroxy-benzphetamine glucuronide (pHBZG), which are urinary metabolites of benzphetamine, in humans. Urine samples were hydrolysed with beta-glucuronidase (EC 3.2.1.31) at 37 degrees C overnight and the treated urine was applied to a solid phase extraction column. After washing the column with water, 0.01 mol/L acetic acid and methanol, pHBA and pHBZ were eluted with dichloromethane:isopropanol:28% ammonium hydroxide (78.4:19.6:2.0 v/v). The eluate was evaporated and the residue was dissolved in acetonitrile: 5 mmol/L 1-pentane sulphonic acid (5:95 v/v) and analysed by HPLC with gradient elution. The amounts of urinary pHBAG and pHBZG excreted by two human subjects after oral administration of 10 mg benzphetamine hydrochloride were determined. About 10-15% of benzphetamine was found to be excreted as pHBAG and pHBZG, and almost all of these metabolites were excreted within 24 h. Urine samples should be collected as early as possible after ingestion of benzphetamine to detect pHBAG and pHBZG.

Detection of amphetamine and methamphetamine following administration of benzphetamine.

Interpretation of urine drug-testing results is a challenging endeavor for several reasons. Effects of pH, dilution, legitimate and illicit sources of the drugs, and, perhaps the most challenging, the possibility of the methamphetamine and/or amphetamine being the result of the use of some other drug. Although it is known that 14 different compounds are metabolized to methamphetamine or amphetamine or both, there is little information on the metabolic profile of many of these compounds, making interpretation of results difficult. Benzphetamine, administered as a single Didrex tablet, was given to 10 subjects (7 male and 3 female) and urine samples collected for the next 7 days. Gas chromatography-mass spectrometry results showed 3 of the 10 subjects did not have a single urine sample that exceeded a 500-ng/mL cutoff for amphetamine or methamphetamine. The other subjects had between one and six samples that tested positive at or above that level. Two subjects excreted more methamphetamine than amphetamine, whereas the other eight excreted greater amounts of amphetamine than methamphetamine. The observed ratio between amphetamine and methamphetamine was significantly different than what would be expected from the use of methamphetamine. Results of this study indicate the metabolism of benzphetamine to desmethylbenzphetamine is a major pathway in the metabolism of the drug. Enantiomer analysis of the methamphetamine and amphetamine revealed only the d-enantiomer. Results of this study add significant information useful to interpret the possibility of benzphetamine as the origin of methamphetamine and amphetamine in urine samples.

The metabolism of 1-phenyl-2-(N-methyl-N-benzylamino)propane (benzphetamine) and 1-phenyl-2-(N-methyl-N-furfurylamino)propane (furfenorex) in man.

The metabolic fate of 1-phenyl-2-(N-methyl-N-benzylamino)propane (benzphetamine) and 1-phenyl-2-(N-methyl-N-furfurylamino)propane (furfenorex) in healthy volunteers has been investigated. Nine metabolites with traces of the unchanged drug were detected in human urine after oral administration of benzphetamine, and five metabolites were found following administration of furfenorex. The major metabolites were 1-(p-hydroxyphenyl)-2-(N-benzylamino)propane for benzphetamine and 1-phenyl-2-(N-methyl-N-gamma-valerolactonylamino)propane for furfenorex. In both cases, methamphetamine, amphetamine and their hydroxylated metabolites were also excreted as minor metabolites. Identified metabolites excreted in three days after administration of benzphetamine accounted for 30-44% of the dose and those excreted after administration of furfenorex, 31-46%.

Enhancement in vivo of drug oxidations following administration of benzphetamine, acetone, metyrapone and dimethylsulfoxide.

Effects of benzphetamine, acetone, metyrapone and dimethylsulfoxide administration to rats on the metabolism of drugs by liver 9,000 x g supernatant fraction were studied herein. Activities for aniline hydroxylation and phenacetin O-deethylation were increased while ethylmorphine and benzphetamine N-demethylations were unchanged by the single administration of acetone, metyrapone or dimethylsulfoxide. Increase in aniline hydroxylase activity by about 53.4% and in phenacetin O-deethylase activity by about 44.4% were observed at 30 min after the single administration of benzphetamine whereas ethylmorphine N-demethylase activity was slightly decreased. NADPH-cytochrome P-450 reductase activity and cytochrome P-450 content were unaltered until 12 hr after the single administration of benzphetamine. Aniline hydroxylation was increased by the addition of benzphetamine to the incubation mixture and the increase in aniline hydroxylation caused by benzphetamine could be reversed by washing the microsomes.