The metabolism of 1-phenyl-2-(N-methyl-N-furfurylamino)propane (furfenorex) in the rat in vivo and in vitro.

The metabolism of 1-phenyl-2-(N-methyl-N-furfurylamino)propane (furfenorex) was studied in the rat in vivo and in vitro. Nine metabolites with only traces of the unchanged drug were obtained from urine after oral administration of furfenorex to rats. The major metabolite was an acidic compound, isolated and identified as 1-phenyl-2-(N-methyl-N-gamma-valerolactonylamino)propane. Amphetamine, methamphetamine and their hydroxylated metabolites were excreted as minor metabolites. Metabolites excreted in two days after administration of the drug amounted to about 20% of dose. The acidic metabolite, a major metabolite in vivo, was not detected after incubation of furfenorex with rat-liver microsomes. The major metabolic routes of furfenorex in vitro were N-demethylation and N-defurfurylation which produced 1-phenyl-2-(N-furfurylamino)propane (furfurylamphetamine) and methamphetamine, respectively. The formation of furfurylamphetamine and methamphetamine were catalysed by rat-liver microsomes supplemented with NADPH and O2, and were inhibited by either SKF 525-A or CO. The formation of both metabolites were inhibited by 2-methyl-1,2-bis-(3-pyridyl)-1-propanone (metyrapone), but not by 7,8-benzoflavone. They were enhanced by pretreatment of rats with phenobarbitone, but not with 3-methylcholanthrene. These data suggested that N-demethylation and N-defurfurylation of furfenorex were mainly mediated by cytochrome P-450 but not cytochrome P-448.

Determination of nitrazepam and its main metabolites in urine by thin-layer chromatography and direct densitometry.

A method for the direct quantitative densitometry of nitrazepam and its main metabolites (7-aminonitrazepam, 7-acetamidonitrazepam and 2-amino-5-nitrobenzophenone) in urine was developed. The unchanged drug and its metabolites were extracted with benzene-dichloromethane (4:1), subjected to thin-layer chromatography, and determined by direct ultraviolet densitometry. Recovery experiments showed that the method was quantitative. The limit of detection was 5 ng/ml for 2-amino-5-nitrobenzophenone and 10 ng/ml for other compounds. The method was applied to the determination of nitrazepam and its metabolites excreted in human urine after administration of 10 mg of the drug.

Distribution and excretion of methamphetamine and its metabolites in rats. III. Time-course of concentrations in blood and bile, and distribution after intravenous administration.

The time-course of blood total radioactivity after i.v. administration of 3H-methamphetamine to rats showed a biphasic curve. The biological half-life of the alpha phase (t alpha 1/2) was 6.8 +/- 2.0 min, and that of the beta phase (t beta 1/2) was 11.3 +/- 0.8 h. The major metabolite in the blood was unconjugated p-hydroxymethamphetamine. The total radioactivity in bile peaked at 1.5 h after i.v. administration. The major metabolite in the bile was p-hydroxymethamphetamine glucuronide. The major compound excreted in urine was unchanged methamphetamine. Whole-body autoradiography was performed using 14C-methamphetamine, and tissue 3H concn. was determined after i.v. administration of 3H-methamphetamine to rats.

Distribution and excretion of methamphetamine and its metabolites in rats. II. Time-course of concentration in blood and distribution after multiple oral administration.

The time-course of total blood radioactivity after oral administration of 3H-methamphetamine, following multiple oral administration of non-radioactive methamphetamine for 7 and 14 days to rats, was examined to elucidate the effects of multiple administration on enterohepatic circulation. Whole-body autoradiographs of rats after oral administration of 14C-methamphetamine showed high levels of radioactivity in contents of stomach and small intestine, bladder urine, liver, and various glands. Distribution of methamphetamine and the major metabolite in tissues during multiple dosing was investigated; accumulation occurred in brain, liver, testis and fat. Multiple oral administration of methamphetamine to rats slightly induced enzyme activities of N-demethylation and aromatic hydroxylation of methamphetamine in rat-liver 9000 g supernatant.

Rapid screening method for methamphetamine in urine by colour reaction in a Sep-Pak C18 cartridge.

A simple screening method for methamphetamine in urine by colour reaction was developed. Methamphetamine, which is quantitatively retained in a Sep-Pak C18 cartridge, is (after a clean-up procedure) coloured by Simon's reagent (consisting of sodium nitroprusside solution, sodium carbonate solution and acetaldehyde gas). The detection limit was 0.5 microgram/ml using 5 ml of urine sample. The results of the screening method agreed with those of thin-layer chromatography and gas chromatography-mass spectrometry.

The metabolism of 1-phenyl-2-(N-methyl-N-benzylamino)propane (benzphetamine) in vitro in rat.

The metabolism of 1-phenyl-2-(N-benzylamino)propane (benzphetamine) in vitro was studied using rat-liver microsomes. Five metabolites were isolated from the incubation mixture and identified as 1-phenyl-2-(N-benzylamino)propane (benzylamphetamine), (1-(p-hydroxyphenyl)-2-(N-methyl-N-benzylamino)propane, 1-(p-hydroxyphenyl)-2-(N-benzylamino)propane, methamphetamine and amphetamine. This metabolism in vitro was compared with that in vivo which was reported previously. The formation of all five metabolites were catalysed by liver microsomes supplemented with NADPH and O2, and inhibited by either SKF 525-A or CO. N-Demethylation was inhibited by either 2-methyl-1,2-bis-(3-pyridyl)-1-propanone (metyrapone) or n-octylamine, while aromatic hydroxylation was inhibited by 7,8-benzoflavone and N-debenzylation was depressed by all these inhibitors. N-Demethylation was enhanced by pretreatment of rats with phenobarbitone, while aromatic hydroxylation was induced by pretreatment with 3-methylcholanthrene, and N-debenzylation was Induced by pretreatment with either phenobarbitone or 3-methylcholanthrene. These data suggested that the metabolism of benzphetamine was mediated by three slightly different enzyme systems.

Determination of methamphetamine in hair after single and repeated administration to rat.

Methamphetamine in hair after p.o. administration to rat was identified and determined by mass fragmentography (MF). Rat hair was washed with HCl/methnanol, methanol and water. The hair was crushed in 0.6 M HCl, suspension was alkalized with Na2CO3, and extracted with chloroform/isopropanol. The extract obtained was purified by column chromatography on aluminium oxide. Concentrated eluate was trifluoroacetylated, and methamphetamine was identified and determined by MF. More than 20 pg of methamphetamine was detectable and less than 1 ng of that was determined by MF. Methamphetamine in hair collected from rat after p.o. administration of 20 mg/kg of the drug was detected and determined up to 8 days after. From hair of rat after 5-days or 14-days repeated administration of 20 mg/kg/day, methamphetamine was detected 25 or 45 days after the last administration, respectively.

The metabolism of 1-phenyl-2-(N-methyl-N-benzylamino)propane (benzphetamine) in vivo in the rat.

1. The metabolism of 1-phenyl-2-(N-methyl-N-benzylamino)propane (benzphetamine) was studied in vivo in the rat. 2. Nine metabolites were obtained from urine after oral administration of benzphetamine to rats. The major metabolite, identified as 1-(p-hydroxyphenyl)-2-(N-benzylamino)propane, was formed by aromatic hydroxylation and N-demethylation. One of the minor metabolites was methamphetamine, formed by N-debenzylation. 3. Metabolites excreted in three days after administration of the drug amounted to about 40% of the dose.

Determination of d-methamphetamine in urine after administration of d- or dl-methamphetamine to rats by radioimmunoassay using optically sensitive antiserum.

A radioimmunoassay was developed for the determination of d-methamphetamine in urine. Antiserum to d-methamphetamine was prepared in rabbits by immunization with d-N-4-aminobutylmethamphetamine conjugated with bovine serum albumin. d-1-[3H]-Methamphetamine was used as a labeled compound for radioimmunoassay. The specificity of the antibody against d-methamphetamine was determined by cross-reaction studies with optical isomers of methamphetamine and its analogs. The antibody was specific for d-methamphetamine and exhibited no significant cross-reaction with the l-isomers. This stereoselective assay was applied to determination of d-methamphetamine excreted in urine after oral administration of d- or dl-methamphetamine to rats.

Distribution and excretion of methamphetamine and its metabolites in rats. I. Time-course of concentrations in blood and bile after oral administration.

1. Concentration time-courses of methamphetamine and its metabolites in the blood after oral administration of [3H]methamphetamine to rats showed two distinct peaks at 2.5 and 8 h after dosing. The major metabolite present in the blood at all times was unconjugated p-hydroxymethamphetamine. 2. Biliary excretion of radioactivity after oral administration of [3H]methamphetamine to rats was about 30% dose in 24h. The major metabolite in the bile was p-hydroxymethamphetamine glucuronide. 3. Blood and bile were collected simultaneously from a rat fitted with a T-tube cannula in the common bile duct, and time-courses of blood and bile concn. of the drug and metabolites were investigated. The observation of two peaks in both blood and bile indicates enterohepatic circulation of the drug and metabolites.

Effects of inducers and/or inhibitors on metabolism of lysergic acid diethylamide in rat liver microsomes.

1. When lysergic acid diethylamide (LSD) was incubated with liver microsomes obtained from untreated rats, SKF 525-A inhibited most potently the hydroxylation at the 13-position, moderately inhibited N-demethylation at the 6-position, and least affected the metabolism of the side-chain at the 8 position. Furthermore, an atmosphere of 80% CO and 20% O2 (v/v) caused max. inhibition in N-demethylation, moderate inhibition in 13-hydroxylation, and the minimum in metabolism of the side-chain at the 8-position. These data suggested that the metabolism of LSD is catalysed by three separate enzyme systems. 2. The formation of 13-hydroxy-lysergic acid diethylamide (13-hydroxy-LSD) in liver microsomes obtained from 3-methylcholanthrene-treated rats was not inhibited by CO, although the hydroxylation required NADPH and oxygen. 3. The results of experiments using various inhibitors suggest that the 13-hydroxylation in liver microsomes from 3-methylcholanthrene-treated rats is catalysed by an enzyme system involving an unusual type of cytochrome P-448.

Enzymic formation of dehydrogenated and hydroxylated metabolites from lysergic acid diethylamide by rat liver microsomes.

1. The metabolism of lysergic acid diethylamide (LSD) was studied using rat liver microsomes, and two minor metabolites were obtained in addition to lysergic acid ethylamide and N6-desmethyl-lysergic acid diethylamide (nor-LSD) which were reported previously. 2. One of the metabolites was identified as lysergic acid ethylvinylamide, apparently formed by dehydrogenation of a diethylamide group in the side chain at the 8-position, and the other as the phenol 13-hydroxy-LSD. 3. The formation of both lysergic acid ethylamide and lysergic acid ethylvinylamide was similarly induced by pretreatment of rats with either phenobarbitone sodium or 3-methylcholanthrene, while nor-LSD formation was induced only by phenobarbitone and that of 13-hydroxy-LSD only by methylcholanthrene.

Excretion of methoxyphenamine and its metabolites in rat urine.

Metabolites of methoxyphenamine in urine obtained after oral administration of the drug to rats have been isolated by Sephadex LH-20 column chromatography and identified as the O-, N,O- and N-demethylated derivatives of methoxyphenamine by thin-layer chromatography, spectrometry, and comparisons with synthesized compounds. The unchanged drug and the metabolites excreted in urine have been extracted and determined by gas chromatography after treatment with trifluoroacetic anhydride.