Piperazine-Derived Designer Drug 1-(3-Chlorophenyl)piperazine (mCPP): GC-MS Studies on its Metabolism and its Toxicological Detection in Rat Urine Including Analytical Differentiation from its Precursor Drugs Trazodone and Nefazodone*

Studies on the metabolism and the toxicological analysis of the piperazine-derived designer drug 1-(3-chlorophenyl)piperazine (mCPP) in rat urine using gas chromatography-mass spectrometry (GC-MS) are described. mCPP was extensively metabolized, mainly by hydroxylation of the aromatic ring and by degradation of the piperazine moiety to the following metabolites: two hydroxy-mCPP isomers, N-(3-chlorophenyl)ethylenediamine, 3-chloroaniline, and two hydroxy-3-chloroaniline isomers. The hydroxy-mCPP metabolites were partially excreted as the corresponding glucuronides and/or sulfates, and the aniline derivatives were partially acetylated to N-acetyl-hydroxy-3-chloroaniline isomers and N-acetyl-3-chloroaniline. Our systematic toxicological analysis (STA) procedure using full-scan GC-MS after acid hydrolysis, liquid-liquid extraction, and microwave-assisted acetylation allowed the detection of mCPP and its previously mentioned metabolites in rat urine after single administration of a dose calculated from the doses commonly taken by drug users. The hydroxy-mCPP metabolites should be used as target analytes being the major metabolites of mCPP. Assuming similar metabolism, our STA procedure should be suitable for detection of an intake of mCPP in human urine. Furthermore, possibilities for differentiating an intake of mCPP from that of its precursor drugs trazodone or nefazodone, two common antidepressants, are described. Within the context of these studies, N-(3-chlorophenyl)ethylenediamine was identified as a new metabolite of these two antidepressants.

The disposition of voriconazole in mouse, rat, rabbit, guinea pig, dog, and human

Voriconazole is a new triazole antifungal agent with potent, wide-spectrum activity. Its pharmacokinetics and metabolism have been studied in mouse, rat, rabbit, dog, guinea pig, and humans after single and multiple administration by both oral and intravenous routes. Absorption of voriconazole is essentially complete in all species. The elimination of voriconazole is characterized by non-linear pharmacokinetics in all species. Consequently, pharmacokinetic parameters are dependent upon dose, and a superproportional increase in area under the curve is seen with increasing dose in rat and dog toxicology studies. Following multiple administration, there is a decrease in systemic exposure. This is most pronounced in mouse and rat, less so in dog, and not observed in guinea pig or rabbit. Repeat-dose toxicology studies in mouse, rat, and dog have demonstrated that induction of cytochrome P450 by voriconazole (autoinduction of metabolism) is responsible for the decreased exposure in these species. Autoinduction of metabolism is not observed in humans, and plasma steady-state concentrations remain constant with time. Voriconazole is extensively metabolized in all species. The major pathways in humans involve fluoropyrimidine N-oxidation, fluoropyrimidine hydroxylation, and methyl hydroxylation. Also, N-oxidation facilitates cleavage of the molecule, resulting in loss of the fluoropyrimidine moiety and subsequent conjugation with glucuronic acid. Major pathways are represented in animal species. The major circulating metabolite in rat, dog, and human is the N-oxide of voriconazole. It is not thought to contribute to efficacy since it is at least 100-fold less potent than voriconazole against fungal pathogens in vitro.

Pharmacokinetics of rizatriptan in healthy elderly subjects

OBJECTIVE

Rizatriptan is a serotonin 5-HT1B/1D receptor agonist for acute treatment of migraine. Its pharmacokinetics were assessed in healthy elderly males and females receiving a single 10 mg tablet oral dose. The pharmacokinetic data (AUC(0-infinity) and Cmax) for the elderly in this study were compared with historical data from previous studies for healthy young adults (n = 65).

METHODS

In a double-blind, parallel, placebo-controlled study, healthy elderly female and male subjects aged 65 or older (n = 8 each) received a single oral dose of 10 mg rizatriptan. Plasma and urine concentrations of drug were determined by HPLC with tandem mass spectrometry detection at several collection time points or intervals starting at predose and postdose over 24 h.

RESULTS

In elderly subjects, the geometric mean values for AUC(0-infinity) and Cmax were 77.7 ng/h/ml and 21.9 ng/ml; the average values for tmax, half-life (t 1/2), renal clearance (Clr), and percent urinary excretion of dose (Ue) were 1.2 h, 1.8 h, 197 ml/min and 9.3%, respectively. The AUC(0-infinity) and Cmax of rizatriptan were similar in elderly and young subjects. The geometric mean AUC ratio of elderly to young was 0.96 with 90% confidence interval (0.83, 1.11), p > 0.25. The geometric mean Cmax ratio was 0.89 with 90% confidence interval (0.72, 109), p > 0.25. No significant pharmacokinetic differences were observed between elderly males and females.

CONCLUSIONS

The plasma pharmacokinetics of rizatriptan appear to be similar in the elderly and young. In the elderly, the pharmacokinetics of rizatriptan do not appear to differ between male and female to a clinically significant extent.

Practical aspects of liquid chromatography/electrospray tandem mass spectrometry for rapid identification of metabolites of a new antifungal agent SYN-2836 in dog urine

This report presents the structural elucidation of 12 urinary metabolites of SYN-2836, a new antifungal agent showing extensive metabolism in beagle dogs, using complementary liquid chromatography/tandem mass spectrometry (LC/MS/MS) methodologies. The 12 SYN-2836 metabolites were readily divided into four groups by considering that all three members of each group, although differing in masses, exhibited highly similar product ion mass spectra. This suggests that the metabolites within each group share a common major substructure. Therefore, all the grouped SYN-2836 metabolites were strategically identified by characterization of the major substructures followed by determination of the additional small substructures. This grouping strategy greatly facilitated the structural elucidation of these metabolites. Other strategies were also employed to achieve as rapid and unambiguous characterization of the SYN-2836 metabolites as possible.

Disposition and pharmacokinetics of the antimigraine drug, rizatriptan, in humans

The absorption and disposition of rizatriptan (MK-0462, Maxalt(TM)), a selective 5-HT(1B/1D) receptor agonist used in the treatment of migraine headaches, was investigated in humans. In a two-period, single i.v. (3 mg, 30-min infusion), and single oral (10 mg) dose study with [(14)C]rizatriptan in six healthy human males, total recovery of radioactivity was approximately 94%, with unchanged rizatriptan and its metabolites being excreted mainly in the urine (89% i.v. dose, 82% p.o. dose). Approximately 26 and 14% of i.v. and oral rizatriptan doses, respectively, were excreted in urine as intact parent drug. In a second, high-dose study (60 mg p.o.), five metabolites excreted into urine were identified using liquid chromatography-tandem mass spectrometry and NMR methods. They were triazolomethyl-indole-3-acetic acid, rizatriptan-N(10)-oxide, 6-hydroxy-rizatriptan, 6-hydroxy-rizatriptan sulfate, and N(10)-monodesmethyl-rizatriptan. Urinary excretion of triazolomethyl-indole-3-acetic acid after i.v. and oral administrations of rizatriptan accounted for 35 and 51% of the dose, respectively, whereas the corresponding values for rizatriptan-N(10)-oxide were 4 and 2% of the dose. Plasma clearance (CL) and renal clearance (CL(r)) were 1325 and 349 ml/min, respectively, after i.v. administration. A similar CL(r) value was obtained after oral administration (396 ml/min). The primary route of rizatriptan elimination occurred via nonrenal route(s) (i.e., metabolism) because the CL(r) of rizatriptan accounted for 25% of total CL. Furthermore, the CL(r) was higher than normal glomerular filtration rate ( approximately 130 ml/min), indicating that this compound was actively secreted by renal tubules. The absorption of rizatriptan was approximately 90%, but it experienced a moderate first-pass effect, resulting in a bioavailability estimate of 47%.

Structure elucidation of three isomeric metabolites of SYN-2836, a novel antifungal agent, in dogs via liquid chromatography/mass spectrometry and liquid chromatography/tandem mass spectrometry methodologies

This paper presents liquid chromatography/mass spectrometry (LC/MS) and liquid chromatography/tandem mass spectrometry (LC/MS/MS) approaches for the rapid characterization of three urinary isomeric metabolites and their two precursor metabolites of SYN-2836, a novel antifungal agent, in dogs administered multiple oral doses of the agent (30 mg kg(-1) day(-1)). A collection of correlative data regarding the SYN-2836 metabolites was obtained by LC/MS and LC/MS/MS performed under complementary conditions such as the columns (C(18) vs cyano type), the mobile phase systems (acetonitrile-water-formic acid vs acetonitrile-water-ammonium acetate) and the electrospray ionization modes (positive vs negative). Metabolite identification was accomplished based on not only the LC/MS/MS data (product ion spectra) but also the LC/MS data indicating chromatographic behaviors of the metabolites. SYN-2836 and SYN-2869, an analog of the former, showed almost the same metabolic pathways following the same multiple-dose administration of the individual agents to the dogs. Therefore, correlation analysis in product ion spectra between corresponding metabolites of SYN-2836 and SYN-2869, and also in metabolic pathways between the two agents, was strategically used to facilitate the identification of the SYN-2836 (and SYN-2869 if necessary) metabolites. For the reason that various elucidation strategies were used complementarily, the chemical structures of the metabolites were unambiguously attained and the isomeric metabolites were explicitly differentiated without the use of other analytical methods. The methodologies used in this study may be applicable to metabolite screening of several structurally related agents simultaneously, promoting lead finding and optimization of drug candidates using a metabolism-based approach.

Biological monitoring of the fungicide epoxiconazol during application

A method was developed for the biological monitoring of the fungicide epoxiconazol (Opus; BASF). Comparison of the urine levels of a hydroxylated metabolite after dermal application to the levels after oral intake revealed a dermal absorption of 1-2.5% of the dose. In a field study with 10 applicators a dermal exposure ranging between 60 and 10,000 microgram/person/day was determined from the urine levels of a hydroxylated metabolite; the contribution of the inhalation exposure was found to be negligible. From these data an incorporation of 1 to 100 microgram epoxiconazol/person/day could be derived. The measured exposure was compared to two commonly used exposure models. The model calculation resulted in a dermal exposure of 555 microgram/person/day (German BBA model) and 2115 microgram/person/day (British POEM), respectively, which is in accordance with the actually measured exposure.

Determination of the anti-platelet-activating factor BN-50727 and metabolites in human urine by high-performance liquid chromatography using solid-phase extraction

A sensitive and selective HPLC solid-phase extraction procedure was developed for the determination of platelet-activating factor antagonist BN-50727 and its metabolites in human urine. The procedure consisted in a double solid-phase extraction of the urine samples on cyanopropyl and silica cartridges, followed by an automated solid-phase extraction of the drug and metabolites on CBA cartridges and posterior elution on-line to the chromatographic system for its separation. The method allowed quantitation in the concentration range 10-2400 ng/ml urine for both BN-50727 and the main metabolite, the O-demethylated BN-50727 product. The limit of quantitation for both compounds was 10 ng/ml. The inter-assay precision of the method, expressed as relative standard deviation, ranged from 1.9 to 4.5% for BN-50727 and from 2.5 to 9.0% for the metabolite. The accuracy, expressed as relative error, ranged from -2.4 to 4.2% and from 0.2 to 6.2%, respectively. This paper describes the validation of the analytical methodology for the determination of BN-50727 in human urine and also for its metabolites. The method has been used to follow the time course of BN-50727 and its metabolites in human urine after single-dose administration.

Triazolines--XXVII. delta2-1,2,3-triazoline anticonvulsants: novel 'built-in' heterocyclic prodrugs with a unique 'dual-action' mechanism for impairing excitatory amino acid L-glutamate neurotransmission

The delta2-1,2,3-triazoline anticonvulsants (1) may be considered as representing a unique class of 'built-in' heterocyclic prodrugs where the active 'structure element' is an integral part of the ring system and can be identified only by a knowledge of their chemical reactivity and metabolism. Investigations on the metabolism and pharmacology of a lead triazoline, ADD17014 (1a), suggest that the triazolines function as 'prodrugs' and exert their anticonvulsant activity by impairing excitatory amino acid (EAA) L-glutamate (L-Glu) neurotransmission via a unique 'dual-action' mechanism. While an active beta-amino alcohol metabolite, 2a, from the parent prodrug acts as an N-methyl-D-aspartate (NMDA)/MK-801 receptor antagonist, the parent triazoline impairs the presynaptic release of L-Glu. Various pieces of theoretical reasoning and experimental evidence led to the elucidation of the dual-action mechanism. Based on the unique chemistry of the triazolines, the potential metabolic pathways and biotransformation products of 1a were predicted to be the beta-amino alcohols 2a and 2a', the alpha-amino acid 3a, the triazole 4a, the aziridine 5a, and the ketimine 6a. In vivo and in vitro pharmacological studies of 1a and potential metabolities, along with a full quantitative urinary metabolic profiling of 1a, indicated the beta-amino alcohol 2a as the active species. It was the only compound that inhibited the specific binding of [3H]MK-801 to the MK-801 site, 56% at 10 microM drug concentration, but itself had no anticonvulsant activity, suggesting 1a acted as a prodrug. Three metabolites were identified; 2a was the most predominant, with lesser amounts of 2a', and very minor amounts of aziridine 5a. Since only 5a can yield 2a', its formation indicated that the biotransformation of 1a occurred, at least in part, through 5a. No amino acid metabolite 3a was detected, which implied that no in vivo oxidation of 2a or oxidative biotransformation of 1a or 5a by hydroxylation at the methylene group occurred. While triazoline 1a significantly decreased Ca2(+)-dependent, K(+)-evoked L-Glu release (83% at 100 microM drug concentration), triazolines 1a-1c showed an augmentation of 50-63%, in the Cl- channel activity, a useful membrane action that reduces the excessive L-Glu release that occurs during epileptic seizures. The high anticonvulsant activity of 1a may be due to its unique dual-action mechanism whereby 1a and 2a together effectively impair both pre- and postsynaptic aspects of EAA neurotransmission, and has clinical potential in complex partial epilepsy which is refractory to currently available drugs.

Pharmacokinetics and metabolism of genaconazole, a potent antifungal drug, in men

The pharmacokinetics of genaconazole, a racemic triazole antifungal agent comprising 50% RR and 50% SS enantiomers, were studied in 12 healthy male volunteers after a single oral dose of 200 mg. The serum samples were analyzed for the two enantiomers by using a chiral high-pressure liquid chromatography assay. The concentrations of the RR and SS enantiomers in serum were virtually identical. The mean values for the maximum concentrations in serum (Cmax) (1.7 micrograms/ml), times to Cmax (4.0 to 4.2 h), half-lives (83 h), and areas under the concentration-time curve from 0 h to infinity (195 to 199 micrograms.h/ml) were similar for the two enantiomers. The results showed that the pharmacokinetic profiles of the two enantiomers were similar after a single oral dosing of the racemate. The pharmacokinetics of the RR enantiomer were also evaluated in 12 healthy male volunteers after a single oral dose of 100 or 200 mg. The ratios of the Cmaxs and of the areas under the concentration-time curves from 0 h to infinity for the two doses were about 2, indicating a dose proportionality. In a separate study, six healthy male volunteers received a single oral dose of 50 mg of 14C-labeled genaconazole. The Cmax values for total radioactivity (14C) and intact genaconazole were virtually identical (0.6 micrograms/ml). The mean half-lives in serum were about 73 h for both total radioactivity and genaconazole. The amounts of total radioactivity excreted in the 0 to 240-h interval (representing approximately three half-lives) in urine and feces were 66.6 and 9.3% of the dose, respectively; 64.4% of the dose was excreted in urine as parent drug. There were no detectable metabolites in either serum or urine. The data demonstrate that genaconazole (racemate) is well absorbed, undergoes negligible biotransformation, and is slowly excreted, primarily in the urine.

Steady-state pharmacokinetics of nefazodone in subjects with normal and impaired renal function

The steady-state pharmacokinetics of nefazodone (NEF) and its metabolites hydroxynefazodone (HO-NEF) and m-chlorophenylpiperazine (mCPP) were compared in subjects with normal and impaired renal function.

PATIENTS

The Study was of parallel group design which included 7 subjects with normal (NOR) renal function, CLCR > or = 72 ml.min-1 x 1.73 m-2, 6 with moderate (MOD) renal impairment, CLCR 31-60 ml.min-1 x 1.73 m-2 and 9 with severe (SEV) renal impairment, CLCR < or = 30 ml.min-1 x 1.73 m-2. Subjects in each renal function group received a 100-mg oral dose of nefazodone hydrochloride BID for 7 days and a single morning dose on day 8. Starting 48 h after the last 100-mg dose, 200-mg doses were administered on a similar schedule to 3, 4 and 3 subjects from each renal function group (NOR, MOD and SEV, respectively). Single trough blood samples just prior to each morning dose (Cmin) and serial samples after the dose on day 8 were obtained at each dose level for pharmacokinetic analysis. Plasma samples were assayed by a specific HPLC method for NEF, HO-NEF and mCPP. The CMIN data indicated that steady state was attained by the third day of BID administration of both the 100- and 200-mg doses of nefazodone, regardless of degree of renal function. Both NEF and HO-NEF attained steady-state Cmax within 2 h after administration of nefazodone; tmax for mCPP was less defined and more delayed. HO-NEF and mCPP plasma levels were about 1/3 and < 1/10 those of NEF, respectively, regardless of the status of renal function. Steady-state systemic exposure of NEF and HO-NEF, as reflected by AUC and Cmax, and elimination t1/2 values did not differ significantly among renal function groups.

CONCLUSION

The study results suggest that dose adjustments may not be necessary, but nefazodone should be used with caution in the presence of severe renal impairment.

Automated analysis of a novel anti-epileptic compound, CGP 33,101, and its metabolite, CGP 47,292, in body fluids by high-performance liquid chromatography and liquid-solid extraction

Automated procedures for the determination of CGP 33,101 in plasma and the simultaneous determination of CGP 33,101 and its carboxylic acid metabolite, CGP 47,292, in urine are described. Plasma was diluted with water and urine with a pH 2 buffer prior to extraction. The compounds were automatically extracted on reversed-phase extraction columns and injected onto an HPLC system by the automatic sample preparation with extraction columns (ASPEC) automate. A Superlosil LC-18 (5 microns) column was used for chromatography. The mobile phase was a mixture of an aqueous solution of potassium dihydrogen phosphate, acetonitrile and methanol for the assay in plasma, and of an aqueous solution of tetrabutylammonium hydrogen sulfate, tripotassium phosphate and phosphoric acid and of acetonitrile for the assay in urine. The compounds were detected at 230 nm. The limit of quantitation was 0.11 mumol/l (25 ng/ml) for the assay of CGP 33,101 in plasma, 11 mumol/l (2.5 micrograms/ml) for its assay in urine and 21 mumol/l (5 micrograms/ml) for the assay of CGP 47,292 in urine.

Quantitative measurement of BN50727 in human plasma and urine by combined liquid chromatography/negative ion chemical ionization mass spectrometry using a particle beam interface

A new sensitive assay has been developed for the quantitative measurement of BN50727 at the picomole level in human plasma and urine. The drug and the internal standard (BN50788) were measured by combined liquid chromatography/negative ion chemical ionization mass spectrometry with methane as the reagent gas. A simple solid-liquid extraction procedure was used to isolate BN50727 from the complex biological matrices. The mass spectrometer was tuned to monitor the intense and stable ion at m/z 333 which was generated in the ion source by a dissociative capture process. This assay was performed with 1 ml of plasma or 0.1 ml of urine and the quantification limit of the method was statistically calculated as 1 ng ml-1. The very low relative standard deviations and mean percentages of error calculated during the different within-day or between-day repeatability assays have clearly demonstrated the ruggedness of the technique for the routine determination of BN50727 in biological fluids. Some preliminary results on the pharmacokinetics of the drug are presented to illustrate the applicability of this powerful liquid chromatographic/mass spectrometric method.

Quantitative measurement of a new synthetic hetrazepine derivative, BN50730, in human plasma and urine by combined liquid chromatography-negative chemical ionization mass spectrometry using a particle beam interface

A new simple and sensitive assay has been developed for the quantitative measurement of BN50730 at the picomole level in human plasma and urine. The drug and the internal standard (BN50765) were measured by combined liquid chromatography-negative chemical ionization mass spectrometry with methane as the reagent gas. A simple solid-liquid extraction procedure was used to isolate BN50730 from complex biological matrices. Mild operating conditions were required to assay the parent drug with a particle beam interface from Hewlett-Packard. The mass spectrometer was tuned to monitor the intense ion m/z 333, which was generated in the ion source by a dissociative capture process. This assay was performed with 1 ml of plasma or 0.1 ml of urine, and the quantification limit of the method was statistically calculated as 1 ng ml-1. The very low relative standard deviation and mean percentage of error calculated during the different within-day or between-day repeatability assays clearly demonstrate the ruggedness of the technique for the routine determination of BN50730 in the biological fluids. Some preliminary results on the pharmacokinetics of the drug are presented to illustrate the applicability of this new powerful LC-MS method.

Gas chromatographic and high-performance liquid chromatographic methods for the determination of genaconazole in biological fluids

Gas chromatographic (GC) and high-performance liquid chromatographic (HPLC) methods were developed for the determination of genaconazole in biological fluids. Both methods involved organic solvent extraction followed by solid-phase extraction on a C18 column. GC analysis utilized a megabore column (DB-17) with 63Ni electron-capture detection, whereas HPLC analysis utilized separation on a reversed-phase column with a methanol-phosphate buffer mixture as the mobile phase and quantitation by UV absorbance at 208 nm. Both methods yielded good linearity, accuracy and precision. The limit of quantitation (LOQ) was 0.025 microgram per ml of serum for GC and 0.2 microgram per ml of serum or 0.5 microgram per ml of urine for HPLC analysis. Both GC and HPLC methods were used for the determination of serum concentration-time curves of genaconazole in man following oral administration of a 50-mg dose.

Development, application and comparison of an enzyme immunoassay and a high-performance liquid chromatography method for the determination of the aromatase inhibitor CGS 20,267 in biological fluids

CGS 20,267 is a new potent and selective, nonsteroidal, oral aromatase inhibitor. For its determination in human plasma and urine, an enzyme immunoassay (EIA) and an HPLC method were developed. The EIA showed good precision and accuracy (intra- and interassay variation between 3.0 and 17.7%, recoveries between 81 and 106%) and a quantitation limit of 0.7 nmol/L. A strong cross reactivity of the antibodies with the hydroxy metabolite of CGS 20,267 (CGP 44,645) was observed. The HPLC method showed a quantitation limit in plasma of 28 and 34 nmol/L for CGS 20,267 and CGP 44,645, respectively. For urine, concentrations down to 180 nmol/L (CGS 20,267) and 210 nmol/L (CGP 44,645) could be measured. A cross check between EIA and HPLC on plasma samples from healthy male volunteers or breast cancer patients treated orally with CGS 20,267 revealed an excellent correlation (slope = 0.934, intercept = 26, r = 0.991). However, the EIA measurements of urine samples yielded 3-25 times higher concentrations than those obtained by HPLC. Further, HPLC analysis revealed the presence of CGS 20,267 and cross-reacting metabolites in urine but not in plasma. Therefore, the EIA can only be used for the determination of CGS 20,267 in plasma samples.

Determination of SCH 39304 by megabore capillary gas-liquid chromatography

A gas-liquid chromatographic procedure for determination of SCH 39304 at low nanogram concentrations in serum, cerebrospinal fluid, and urine is presented. The methodology combines a high selectivity and sensitivity nitrogen-specific detector, a gas chromatograph equipped with a capillary "megabore" column, and an internal standard that is very similar in chemical structure to the drug being assayed. This method is suitable for both pharmacokinetic studies as well as for monitoring drug levels in patients receiving SCH 39304 for antifungal treatment.

Characterization of the metabolites of the antidepressant drug nefazodone in human urine and plasma

Metabolism of the antidepressant drug nefazodone was studied in humans after single and multiple 50 and 200 mg oral doses of [14C] nefazodone as part of a single and multiple dose balance study. Deuterium was included in the molecule to facilitate structural characterization of the metabolites by mass spectrometry. Metabolites were isolated from a 0-24 hr pooled urine from three subjects and purified to homogeneity by HPLC. Chemical structures of the metabolites were proposed based on collisionally induced dissociation (CID) and electron impact ionization MS. The profile of radioactivity showed three main urinary metabolites, one of which was a conjugate, and several minor metabolites. The three major metabolites were identified as the phenoxyethyl triazolone propionic acid resulting from N-dealkylation of both nefazodone and hydroxynefazodone (OH-Nef), as well as a corresponding phenoxyethyl triazolone propanol metabolite of N-dealkylated nefazodone, present exclusively as a conjugate. The more polar minor components were not identified. The excretion of total radioactivity in the 24-hr sample was 49% of the dose, of which the identified metabolites comprised 38% of the dose. There was no difference in the qualitative or quantitative urinary profile of the metabolites at 50 or 200 mg dose levels after single or multiple oral dosing. These N-dealkylated metabolites were also present in pooled human plasma samples along with nefazodone, OH-Nef, and an unknown metabolite that was present in plasma in large amounts relative to nefazodone and OH-Nef. This metabolite was isolated from plasma and from a human liver S9 incubation and identified by CID tandem MS and NMR as the triazoledione of nefazodone.(ABSTRACT TRUNCATED AT 250 WORDS)

Metabolic polymorphism of E6123 in rhesus monkey

1. The metabolic polymorphism of a new thienodiazepine platelet activating factor receptor antagonist (E6123) in rhesus monkey was studied in vivo and in vitro. 2. After i.v. dosing of 14C-E6123, the levels of radioactivity in blood, plasma and red blood cells were higher in poor metabolizers (PMs) with AUC(0-24 h) values which were about 1.3-1.5 times higher than those in extensive metabolizers (EMs). 3. After i.v. dosing of 14C-E6123, radioactivity was excreted rapidly by both EMs and PMs. However, EMs excreted the radioactivity mainly in urine whereas, for PMs, radioactivity was excreted fairly equally in urine and faeces. 4. In vivo and in vitro studies demonstrated that the metabolic polymorphism of E6123 in rhesus monkey is caused by a difference in the hydrolysis of an amide side chain. 5. Our results suggested that there are two types of the enzymes which metabolize E6123 by this route in EMs, but only one type in PMs. 6. The low affinity enzyme in EMs might be the same as the enzyme in PMs, indicating that the metabolic polymorphism of E6123 in rhesus monkey could depend on the existence of a high affinity enzyme.

Rapid, high-sensitivity reversed-phase liquid chromatographic assay for 9-chloro-2-(2-furyl) [1,2,4]triazolo[1,5-c]quinazolin-5-imine and its oxo metabolite in plasma using fluorescence detection

A rapid, sensitive and specific assay for 9-chloro-2-(2-furyl) [1,2,4]triazolo[1,5-c]quinazolin-5-imine (I) and its oxo metabolite (II) in plasma was developed and validated employing reversed-phase high-performance liquid chromatography with fluorescence detection. Sample preparation was achieved by a simple ethyl acetate extraction from plasma buffered at pH 10 (0.1 M boric acid-0.1 M potassium chloride). Chromatographic analyses were performed isocratically on a C18 column, with a mobile phase consisting of methanol-0.2 M sodium acetate buffer, pH 5.0 (67:33, v/v). Chromatographic run time was less than 8 min. The assay was linear (r greater than 0.9998) over the concentration range 1.50-10,000 ng/ml for both I and II; for individual studies, curves covering a range of two orders of magnitude were generally employed. Limits of detection for I and II were 0.5 and 1.0 ng/ml, respectively. A preliminary investigation of the plasma concentrations of I and II in the rat following a single 30 mg/kg oral dose demonstrated the applicability of the method for pharmacokinetic studies.

Assay of fluconazole by megabore capillary gas-liquid chromatography with nitrogen-selective detection

A megabore column gas-liquid chromatographic method which uses nitrogen-phosphorus detection was developed for the analysis of fluconazole in plasma, serum, cerebrospinal fluid, or urine. The assay was linear from 0.2 to 200 micrograms/ml and had an average coefficient of variation of 7%. The suitability of the assay for pharmacokinetic studies was demonstrated.

Analysis of a new H2 receptor antagonist, 3-amino-5-[3-[4-(1-piperidinoindanyloxy)]propylamino]-1-methyl-1 H-1,2,4-triazole, in human plasma and urine by high-performance liquid chromatography

A high-performance liquid chromatographic (HPLC) method for the determination of a new H2 receptor antagonist, 3-amino-5-[3-[4-(piperidinoindanyloxy)]propylamino] -1-methyl-1H-1,2,4-triazole (I), in human plasma and urine was developed. The method employs liquid-liquid extraction of the analyte and an internal standard and chromatographic separation using an alkylphenyl-bonded HPLC column. The total time of chromatography was less than 10 min. Sensitivity was 10 ng/ml for the plasma analysis and 1 microgram/ml for the analysis of I from urine. The coefficients of variation, based on interpolated concentrations, were less than 10%. The method was used for more than 5000 samples during clinical pharmacokinetic studies.

Determination of fluconazole in biological fluids by capillary column gas chromatography with a nitrogen detector

Fluconazole concentrations in biological fluids were determined by high-performance gas chromatography. A simple extraction procedure with chloroform, under basic conditions and after the addition of UK-47,265 as the internal standard and with no evaporation stage, was carried out prior to analysis. A solid injector and a 15-m capillary column, coated with a nonpolar phase and connected to a nitrogen-selective detector that afforded an excellent selectivity and sensitivity, constituted the gas chromatographic system. The duration of each analysis was less than 4 min and the minimum detectable serum concentration was 50 ng/mL. In five patients undergoing chronic peritoneal dialysis, the mean serum concentrations +/- SD at 1, 6, and 48 h after the intraperitoneal administration of a single dose of fluconazole were, respectively, 325 +/- 75, 928 +/- 159, and 607 +/- 80 ng/mL.

Structure determination of metabolites of rilmazafone, a 1H-1,2,4-triazolyl benzophenone derivative in monkey urine

1. The metabolism of a new hypnotic 5-[(2-aminoacetamido)methyl]- 1-[4-chloro-2-(o-chlorobenzoyl)phenyl]-N,N-dimethyl-1H-1,2,4-tr iaz ole-3-carboxamide hydrochloride dihydrate (rilmazafone hydrochloride) was studies in female cynomolgus monkeys. 2. The structures of ten urinary metabolites were determined by mass spectrometry, and confirmed by comparison with synthetic authentic compounds. 3. Pathways of metabolism are postulated indicating that rilmazafone is desglycylated and cyclized to M-1, demethylated successively to M-2 and M-3, then hydrolysed to M-4, or hydroxylated at the 4-position of benzodiazepine ring or the p-position of the o-chlorophenyl group.