Abstract
The pharmacokinetics and metabolism of nateglinide were studied in six healthy male subjects receiving a single oral (120 mg) and intravenous (60 mg) dose of [14C]nateglinide in randomized order. Serial blood and complete urine and feces were collected for 120 h post dose. Nateglinide was rapidly (∼90%) absorbed, with peak blood and plasma concentrations at ∼1 h post dose. The maximal plasma concentrations of radioactivity (6360 ngEq/ml) and nateglinide (5690 ng/ml) were comparable, and plasma radioactivity concentrations were about twice those of blood at all times. Oral bioavailability was 72%, indicating only a modest first-pass effect. After either dose, plasma nateglinide concentrations declined rapidly with elimination half-lives of 1.5 to 1.7 h and plasma clearance of 7.4 l/h. Plasma radioactivity was eliminated more slowly with half-lives of 52 and 35 h in plasma and blood, respectively, after the oral dose. The contribution of this more slowly eliminated component to the AUC0-∞ was minor. Nateglinide was extensively metabolized, with excretion predominantly (84–87%) in urine. Only ∼16% of the dose was excreted unchanged in urine after either dosing route. The major metabolites were the result of oxidative modifications of the isopropyl group. Three of these were monohydroxylated, two of which appeared to be diastereoisomers. Additionally, one metabolite with an unsaturation in the isopropyl group and two diol-containing isomers were identified. Glucuronic acid conjugates resulting from direct glucuronidation of the carboxylic acid were also present. The major metabolite in plasma and urine was the result of hydroxylation of the methine carbon of the isopropyl group.
Nateglinide [N-(trans-4-isopropylcyclohexylcarbonyl)-d-phenylalanine] is a novel, highly physiologic, mealtime glucose regulator recently approved for the treatment of type II diabetes mellitus. Nateglinide has a rapid onset and short duration of insulinotropic action that results in reduction of mealtime glucose rise and lowers the postabsorptive potential for hypoglycemia in humans and experimental animals (Fujitani et al., 1996; Hu et al., 1998; Ikenoue et al., 1997a,b; Karara et al., 1999; Hanefeld et al., 2000; Keilson et al., 2000). In contrast to sulfonylureas, nateglinide increases pancreatic β-cell sensitivity to ambient glucose without increasing basal insulin secretion (Morimoto et al., 1998; Karara et al., 1999; Keilson et al., 2000). Recently, the identification, synthesis, and pharmacologic testing of several nateglinide metabolites isolated from urine or bile of rat, dog, and human origin were reported (Takesada et al., 1996; Mihara et al., 1997; Ono et al., 1997). Only one of the identified metabolites (designated M7) that possessed an unsaturation in the isopropyl side chain was found to have activity comparable with nateglinide. Because the previous results pertinent to humans were obtained after a nonradiolabeled dose, the relative contribution of the identified metabolites to the overall disposition of nateglinide in humans was unclear. Therefore, the present study was conducted to obtain a more comprehensive understanding of the absorption, metabolism, disposition, and mass balance in healthy male subjects following an oral and intravenous dose of [14C]nateglinide.
Materials and Methods
Study.
Six healthy, nonsmoking male subjects participated in this two-period, open-label, randomized, crossover study. Institutional review board approval was obtained before study start, and all subjects gave written informed consent before participation. Subjects weighed within −10 to +25% of ideal body weight and had not received investigational drugs within 2 months or radioactivity within 12 months before the study. After predose evaluations, each subject received a 5-mg/ml [14C]nateglinide solution either as a 120-mg (80 μCi) dose orally or a 60-mg (20 μCi) dose infused intravenously over 10 min. After a 3-week washout period, subjects received the radiolabeled dose by the alternative route of administration. No concomitant medication was taken during the study. Serial blood and complete urine and feces were collected at designated intervals for 5 days. Blood samples were promptly centrifuged at 4°C for 15 min (∼800g) to obtain plasma. All samples were stored at −20 ± 10°C until analysis.
Study Medication and Reference Standards.
[14C]Nateglinide was synthesized by the Isotope Laboratory of Novartis Pharmaceuticals (East Hanover, NJ). The14C label was located in the carbonyl of the amide moiety of the molecule as shown in Fig.1. Chemical and radiochemical purities of the labeled material were greater than 99%, as determined by HPLC,1 radio-HPLC, and chiral-HPLC.
Metabolic pathways for [14C]nateglinide in humans.
Asterisk denotes the position of the 14C label in nateglinide.
Radioactivity Measurements.
Aliquots of blood and fecal homogenates were combusted in a sample oxidizer (Packard 307) before liquid scintillation counting (Packard model 2500 or 2700 TR). Plasma and urine aliquots were mixed with Formula 989 (Packard) scintillant and counted (Packard Instrument Co., Meriden, CT).
Analysis of Unchanged Nateglinide.
Plasma concentrations of the parent drug were determined using a validated HPLC method similar to that previously reported (Karara et al., 1999). Briefly, a structurally similar internal standard [N-(trans-4-tertiarybutylcyclo-hexylcarbonyl)-d-phenylalanine] was added to an aliquot (0.5 ml) of each plasma sample, followed by 2 ml of 0.05 M phosphate buffer (pH 6.6). The mixture was loaded on a preconditioned solid phase extraction cartridge (Sep-Pak, Waters, Milford, MA). The cartridge was washed with 2 × 3 ml of water, and analytes were eluted with methanol (5 ml). The methanolic extract was evaporated to dryness. The residue was reconstituted in mobile phase [250 μl, 0.05 M sodium phosphate (pH 6.27)/acetonitrile (65:35, v/v)]. After mixing and centrifugation, an aliquot (150 μl) was analyzed by HPLC. The HPLC analysis was performed with a Supelcosil LC-ABZ (250- × 4.6-mm, 5-μm particle size, Supelco, Bellefonte, PA) column and UV detection at 210 nm. The limit of quantification was 50 ng/ml of plasma. The intra-and interday variabilities were 1.45 and 4.47%, respectively.
Sample Preparation for Characterization of Nateglinide Metabolites.
Pooled oral dose plasma was prepared from samples collected at 1, 2, 4, 6, 8, and 12 h post dose. One ml of plasma from each subject was used to obtain each pool, except for the 12-h pool for which 3 ml of plasma from each subject was used. Each pool was treated similarly as follows. Protein was precipitated by the addition of an equal volume of acetonitrile, followed by sonication for 10 min. The supernatant was isolated and the precipitate was further extracted with 4 ml of methanol. The combined supernatants were concentrated to ∼1 ml by evaporation (∼30°C) under nitrogen, and acetonitrile (2 ml) was added to the residual sample. After centrifugation, the resulting supernatant was concentrated to ∼0.1 ml, 50% methanol/water (0.4 ml) was added, and the sample was analyzed by HPLC. Pooled intravenous samples were prepared from the individual plasma samples at 1, 2, and 4 h post dose. For each time point, equal volumes (2.0 ml for 1 h; 3.0 ml for 2 h and 4 h) from each subject were combined. The pooled samples were processed as described above for the oral dose.
Pooled urine samples representing the 0- to 12-h post dose period were prepared for each subject. The urinary excretion of radioactivity over this period represented ∼97% of the total urinary excretion (0–120 h). Aliquots of 5 ml from the oral dose and 10 ml from the intravenous dose were processed as follows. After application of the aliquots to activated Sep-Pak C18 (Waters) cartridges, the cartridges were washed with water, followed by methanol. The methanolic extracts were concentrated, diluted with 50% methanol/water, and analyzed by HPLC.
Metabolite Analysis by HPLC.
The separation of nateglinide and its metabolites was performed on an Inertsil ODS-2 column (GL Sciences, MetaChem, Torrance, CA; 4.6- × 250-mm, 5-μm particle size) with a Pellicular ODS guard column (Whatman, Clifton, NJ). Elution of nateglinide and metabolites was achieved at a flow rate of 1.0 ml/min. A gradient separation was used with solvent A being 0.02 M ammonium acetate (pH ∼6.0) and solvent B being acetonitrile. The gradient involved the following steps: 0 to 5 min, isocratic at 0% solvent B; 5 to 10 min, linear gradient from 0 to 20% solvent B; 10 to 25 min, isocratic at 20% solvent B; 25 to 35 min, linear gradient from 20 to 35% solvent B; 35 to 40 min, isocratic at 35% solvent B; 40 to 55 min, linear gradient from 35 to 45% solvent B; 55 to 60 min, linear gradient from 45 to 100% solvent B; and 60 to 70 min, isocratic at 100% solvent B. For plasma samples, the elution pattern of radioactive metabolite peaks was determined by collecting the column effluent in scintillation vials every 0.5 min, followed by liquid scintillation counting. For urine samples, the radioactive elution pattern was determined by use of a radioisotope detector (β-RAM, IN/US Systems, Tampa, FL) in the homogeneous counting mode (1.0-ml flow cell). The column effluent (1 ml/min) was mixed with liquid scintillant (Flo-Scint II, 3 ml/min; Packard).
Sample enrichment and metabolite isolation.
The 0- to 6-h urine samples after the 120-mg oral dose from subjects 1 (∼1000 ml) and 5 (∼1400 ml) were enriched by solid-phase extraction. The enrichment was achieved using Sep-Pak C18 Vac 35-ml cartridges containing 10 g of sorbent. Each subject's urine was processed separately for NMR analysis. The solid-phase extraction cartridge was washed and activated by sequential addition of methanol, ethyl acetate, methanol, and deionized water. After application of the urine, the cartridge was washed with water. The applied radioactivity was then eluted with methanol (50 ml), and the effluent was concentrated under nitrogen to ∼1 ml. Metabolite peaks were isolated after separation on a semipreparative HPLC system (Kromasil 100 C18, 10 × 250 mm, 10-μm particle size, Eka Nobel, MetaChem). Gradient elution was achieved with a flow rate of 2.0 ml/min, using the same mobile phase as described above. The gradient steps were as follows: 0 to 5 min, isocratic at 0% solvent B; 5 to 20 min, linear gradient from 0 to 30% solvent B; 20 to 40 min, linear gradient from 30 to 40% solvent B; 40 to 50 min, linear gradient from 40 to 50% solvent B; 50 to 60 min, linear gradient from 50 to 100% solvent B; 60 to 70 min, isocratic at 100% B. Aliquots of the concentrated urine extract were injected, and six radioactive peaks were manually collected, concentrated, and lyophilized before NMR analysis.
NMR Analyses.
A sample of unprocessed human urine (0–6-h collection interval) and each of the six isolated fractions were analyzed. Onflow LC-NMR methodology was used for detection of the aromatic protons during the separation of the unprocessed urine sample (100 μl, containing approximately 5–6 μgEq of drug-related material). Retention times for each metabolite were then calculated and stopflow methodology was used to obtain proton (1H) and total correlation spectroscopy (TOCSY) data. For each of the isolated metabolite fractions, standard NMR experiments (1H TOCSY, heteronuclear multiple quantum correlation-, heteronuclear multiple bond correlation-, and heteronuclear single-quantum coherence-TOCSY) were used for each metabolite. The amounts of isolated metabolites ranged from several hundred μgEq to a few mgEq. Tetramethylsilane was the reference compound. Proton data were measured on a Bruker DMX500 spectrometer at 500.13 MHz for 1H and 125.77 MHz for 13C (Bruker, Newark, DE). For the standard experiments, a triple inverse gradient probe (1H,13C, 15N) was used with the temperature of the sample regulated at 300K using CDCl3 as the solvent. The 90°1H pulse for the probe was 10.3 μs at 6 dB, and the 90° 13C pulse was 10 μs at 0 dB. For the LC-NMR experiments, a triple inverse gradient 4-mm flow probe (1H, 13C,31P) was used, with the temperature of the probe regulated at 300K and a 90° 1H pulse of 7.5 μs at 9 dB. The HPLC system consisted of a Bruker LC22 pump, Bischoff UV detector, and Bruker Peak Sampling Unit. The solvent system was a combination of 0.1% trifluoroacetic acid-D/D2O (solvent A) and 0.1% trifluoroacetic acid-D/CD3CN (solvent B). Proton spectra were recorded using a double solvent suppression pulse sequence, irradiating both the residual HOD and acetonitrile peaks. For LC-NMR spectra, the acetonitrile resonance was set to 2.0 ppm.
Mass Spectrometry Analysis.
The mass spectrometry experiments were performed on a Finnigan MAT TSQ7000 mass spectrometer equipped with electrospray and atmospheric pressure chemical ionization interfaces, operating in the positive mode (Finnigan MAT, San Jose, CA). To confirm the identity of plasma metabolite peaks, the parent drug-related product ions from the analysis of plasma were compared with full scan product ion spectra obtained from the analysis of urine. Product ion spectra were obtained at a collision energy of −23 V with the use of argon (1 mTorr) as the collision gas. Analyses were performed using the atmospheric pressure chemical ionization mode to induce ionization and increase sensitivity. However, due to the known thermal lability of glucuronide conjugates, the electrospray ionization mode was used to analyze for suspected acyl glucuronides. HPLC was performed using a Hewlett Packard 1090A equipped with an automatic divert valve, an Inertsil ODS-2 column (GL Sciences, 4.6 × 250 mm, 5-μm particle size) at 40°C, and a radioactivity detector (β-RAM). The separation conditions were identical to those described under HPLC Analyses.
Pharmacokinetic Analysis.
Individual peak concentrations (Cmax) and the time at which the peak was observed (tmax) were recorded for total radioactivity in blood and plasma and nateglinide in plasma. Mean blood radioactivity concentration-time profiles were fitted by polyexponential equations using an iterative nonlinear regression program (PCNONLIN 4.0, SCI Software, Lexington, KY). Plasma clearance (CL) and the steady state volume of distribution (Vss) of nateglinide were estimated using the intravenous data and the following standard equations:
Results
Six subjects entered the study and had a mean age of 30.5 ± 6.1 years (range, 22–37), weight of 80.4 ± 41.3 kg (range, 61.2–101), and body mass index of 28.2 ± 2.8 kg · m−2 (range, 24.5–31.9). Nine minor adverse events occurred in four subjects that did not require treatment or affect study conduct. No clinically significant changes were observed in vital signs, biochemistries, hematologies, and urinalysis. All six subjects completed the study without deviation from the prescribed study procedures.
A single 120-mg oral dose of [14C]nateglinide was rapidly absorbed with a short absorption half-life of 0.22 h (kabs= 3.1 h−1) (Table 1; Fig.2). Radioactivity and nateglinideCmax values were observed approximately 1 h post dose in blood and/or plasma. TheCmax of unchanged drug (5,690 ng/ml) was similar to that of total radioactivity in plasma (6,360 ngEq/ml). Nateglinide accounted for nearly the entire radioactivity in plasma at early time points; however, nateglinide concentrations declined faster than those of total radioactivity. The AUC0-∞of nateglinide in plasma (11,800 ng · h/ml) was approximately 50% of the plasma radioactivity AUC0-∞ value (20,300 ngEq · h/ml). Plasma radioactivity concentrations were approximately twice those in whole blood at all time points.
Pharmacokinetic parameters following a single 60-mg intravenous or 120-mg oral dose of [14C]nateglinide in male subjects
Plasma concentrations of radioactivity (closed circles) and nateglinide (open circles) after a single 60-mg intravenous (10 min) infusion (A) or 120-mg oral dose (B) of [14C]nateglinide in humans.
Results are means ± S.D. from six subjects per group. Curve-fitting results are depicted in log-linear insets.
Following a 60-mg intravenous infusion (10-min duration) of [14C]nateglinide, the highest concentration was observed at 0.25 h after dosing began (5 min post infusion) (Table1; Fig. 2). Nateglinide concentration declined rapidly within 12 h post dose in all subjects, yielding an AUC0-∞of 8,150 ng · h/ml. Similar to the oral dose, plasma radioactivity concentrations were approximately twice those in whole blood at all time points with quantifiable radioactivity levels; the AUC0-∞ values were 12,000 ngEq · h/ml (plasma) and 6,170 ngEq · h/ml (blood).
After oral and intravenous doses, nateglinide was rapidly eliminated from all subjects with a terminal elimination half-life of 1.5 to 1.7 h. Plasma clearance was 7.36 l/h. While nateglinide plasma concentrations declined rapidly, radiolabeled metabolites of nateglinide were eliminated at a more modest rate. The terminal elimination half-life of radioactivity was 52 h in plasma and 35 h in blood following a 120-mg oral dose. The contribution of this component to the overall AUC0-∞, however, was relatively minor: 17 and 13% in plasma and blood, respectively. Data obtained from the intravenous dose was consistent with oral dose data with radioactivity elimination half-lives of 36 h (plasma) and 19 h (blood).
The radioactivity was rapidly excreted primarily in the urine (Table2). More than 70% of the administered radioactivity was excreted within 6 h post dose. Total urinary excretion was 84% (oral dose) and 87% (intravenous dose). Another 8 to 10% of the dose was recovered in the feces yielding nearly complete mass balance within 120 h post dose. Although 84 to 87% of the administered radioactivity was excreted in the urine, unchanged drug represented only 16% of the oral and intravenous doses (Figs. 3 and 4).
Radioactivity excretion (mean ± S.D.)2-a after a single 120-mg oral dose or 60-mg intravenous infusion of [14C]nateglinide in male subjects
Metabolite profiles for nateglinide in human plasma and urine.
Representative profiles after a single oral 120-mg dose. Chemical structures are shown in Fig. 1
Quantitation of nateglinide and metabolites in human urine.
Results shown are means ± S.D. (n = 6 subjects) from pooled samples representing ∼97% of the total urinary excretion.
After oral and intravenous dosing, nine metabolites were characterized in plasma and urine. After either route of administration, the predominant peak in plasma was parent compound and in urine, metabolite M1. Figure 3 shows representative plasma and urinary metabolite patterns following a single oral dose of [14C]nateglinide. The typical retention time for nateglinide in the chromatographic system was 46.5 ± 0.3 min (n = 21). Nateglinide was the major circulating component in plasma at all time points analyzed. Metabolite M1 was the major circulating metabolite, with AUC values of ∼1100 and ∼433 ngEq · h/ml for the oral and intravenous doses, respectively (Table 4). Other metabolites after the oral dose, M11, M12, M2/M3, and M7, had AUC values approximately equal to each other and about half that of M1. The AUC values for the metabolites after an intravenous dose were also less than half the value for M1. The concentrations of metabolites and parent drug in human plasma are summarized in Tables 3 and4.
Relative exposure values for metabolites in plasma following a single oral or intravenous dose of [14C]nateglinide
Plasma concentrations in human after a single dose of [14C]nateglinide3-a
Urinary excretion was the dominant route of elimination (84–87% of the dose) after either dose route, and the urinary metabolites were nearly identical in each case. Regardless of dose route, the urinary excretion of parent drug and metabolite M1 accounted for ∼16 and ∼33% of the dose, respectively (Fig. 4; Table 2). Of the urinary radioactivity, 79 to 83% was associated with the metabolites shown in Table 2. Since the fecal route of elimination was minor, the feces were not analyzed.
Nateglinide metabolism occurs primarily on the isopropyl moiety. Structure elucidation by NMR, LC/NMR, and LC-MS/MS indicated that all but two of the metabolites identified here had been previously isolated and identified from urine and/or bile of animals and humans (Takesada et al., 1996). The MS and NMR results in the present study were in good agreement with this earlier report and are therefore only briefly summarized here.
By mass spectrometry, major metabolite M1 showed an increase of 16 atomic mass units (amu) relative to nateglinide, consistent with monohydroxylation (Table 5). Diagnostic fragments in the product ion spectra suggested that the additional oxygen atom was in the isopropyl-cyclohexyl part of the molecule.1H NMR spectra of M1 revealed a downfield shift of the isopropyl methyl group protons relative to parent drug, as well as a loss of coupling. Additionally, the carbon at the 2-position of the isopropyl group was shifted downfield in the13C spectra. It was therefore concluded that hydroxylation had occurred at the methine position.
Full scan product ion mass spectrometry results
Metabolites M2 and M3 were also monohydroxylated, as indicated by the MS results (Table 5). The NMR spectral findings supported the presence of a hydroxyl on one of the isopropyl methyl groups and the presence of two isomers. From the heteronuclear multiple quantum correlation NMR data, the resulting methylene protons appeared as two doublet of doublets at 3.55 and 3.35 ppm, and the oxygenated methylene carbon was at 64 ppm. Additionally, heteronuclear single-quantum coherence-TOCSY data showed correlations between the methylene and a methyl group.
Metabolite M7 produced a [MH+] two mass units less that nateglinide (Table 5), and 1H NMR analysis indicated the presence of an unsaturation in the isopropyl side chain. The resulting vinylic protons appeared in the region of 4.7 and 1.7 ppm, and the corresponding olefinic carbons were at 120 and 150 ppm, respectively, in the 13C spectra.
Metabolites M11 and M12, which have not been previously reported, showed the addition of 32 amu, suggesting two additional oxygen atoms. Fragmentation in the product ion spectra indicated that the additional oxygens were located in the isopropyl-cyclohexyl portion of the molecule. 1H NMR spectra of these metabolites also revealed a loss of coupling of the isopropyl methyl groups, suggesting a hydroxyl at the methine position. Additionally, the presence of a hydroxyl on one of the methyl groups was indicated by the downfield shift of the remaining two protons and their appearance as an AB pair of doublets at 3.25 and 3.35 ppm. The similarities in spectral data for these metabolites suggested that they are diastereoisomers.
Metabolites M4, M5, and M6 were found to have an increase of 176 amu (MH+ 494; Table 5) and fragmentation consistent with the addition of glucuronic acid. 1H NMR showed the corresponding carbohydrate resonances and indicated the presence of several isomers. Both NMR and MS results indicated the site of glucuronidation was at the carboxylic acid because of little or no changes in the resonances associated with other parts of the molecule. The presence of several isomers was consistent with an acyl glucuronide and the rearrangement products thereof, as had been reported previously (Takesada et al., 1996).
Discussion
Absorption of the 120-mg [14C]nateglinide oral dose began soon after administration, yielding peak radioactivity concentrations within 1 h. Absorption was virtually complete, ∼90%. The bioavailability (f) of the oral dose was 72%, indicating that there was only a modest first-pass effect. The steady state volume of distribution (Vss) of nateglinide measured in plasma, 10.5 l after intravenous dosing, suggests only minimal distribution beyond the plasma volume. Blood-to-plasma radioactivity concentration ratios ranged from 0.47 to 0.56 following the intravenous dose and from 0.52 to 0.74 following the oral dose. No consistent changes in the ratio were noted as a function of time post dose. These ratios indicate that the distribution of nateglinide and its metabolites into blood cells is minimal.
After oral or intravenous dosing in man, nateglinide was metabolized to at least nine metabolites. Of these, seven had been previously reported after isolation from urine and/or bile of rat, dog, and human origin (Takesada et al., 1996). Of the nine metabolites, six were the result of metabolic transformation at the isopropyl side chain, and the major metabolite in plasma and urine was monohydroxylated with the hydroxyl group on the isopropyl methine carbon. No glucuronic acid conjugates of the oxidative metabolites were found. Of the identified metabolites, only M7 possesses significant activity, approximately equal to nateglinide itself (Takesada et al., 1996). However, since the overall exposure to this metabolite after the oral dose is less than 5% that of unchanged drug, the vast majority of the pharmacological effect is attributed to the parent compound. The formation of M7 may occur by either dehydration of monohydroxylated metabolites or more likely via direct dehydrogenation, as has been previously demonstrated for other compounds, such as lovastatin (Vyas et al., 1990) and testosterone (Korzekwa et al., 1990). Diol metabolites, M11 and M12, could be derived from additional hydroxylation of the monohydroxylated metabolites, or from epoxidation of M7, followed by rapid hydrolysis. However, no evidence for an intermediate epoxide was found in the present study. Based on these results, the major metabolic pathways in humans are summarized in Fig. 1.
The fact that nateglinide is mainly excreted as metabolites suggests that metabolism plays an important role in its clearance, with a more minor contribution to clearance coming from renal elimination of unchanged nateglinide. Although the results of the present study do not allow a definitive statement regarding the importance of hepatic metabolism, in vitro experiments with human liver microsomes and heterologously expressed cytochrome P450 isozymes point to CYP2C9 and, to a much lesser extent, CYP3A, as the primary catalysts of oxidative metabolism of nateglinide (J. B. Mangold, unpublished results). The combined involvement of more than one cytochrome P450 in nateglinide metabolism and some renal elimination of unchanged drug decreases the likelihood of drug interactions derived from interference of nateglinide clearance. This prediction is borne out by the lack of clinically significant interactions observed to date (Crick et al., 1999).
In summary, orally administered nateglinide was well absorbed. Unchanged nateglinide was the major circulating component in plasma, and a monohydroxylated metabolite, M1, was the major metabolite in plasma and urine. The major route of elimination of nateglinide and its metabolites was via the urine.
Acknowledgments
We thank Heidi Pfefferkorn for providing the radiolabeled drug substance, Nancy Gary and Betty Juranich for excellent technical assistance, and Dr. Adel Karara for study coordination. The clinical phase of this study was conducted under the supervision of Philip Leese, M.D.
Footnotes
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Send reprint requests to: James B. Mangold, Ph.D., Drug Metabolism and Pharmacokinetics Department, Preclinical Safety, Novartis Institute for Biomedical Research, East Hanover, NJ 07936. E-mail: james.mangold{at}pharma.novartis.com
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This work was presented in part at the 9th North American International Society for the Study of Xenobiotics (ISSX) Meeting in Nashville, TN, Oct. 24–28, 1999.
- Abbreviations used are::
- HPLC
- high-performance liquid chromatography
- AUC0-∞
- area under the plasma concentration-time curve from time zero to infinity
- Cmax
- maximum plasma concentration
- LC-NMR
- liquid chromatography-nuclear magnetic resonance
- TOCSY
- total correlation spectroscopy
- MS
- mass spectrometry
- amu
- atomic mass units
- Received July 24, 2000.
- Accepted December 8, 2000.
- The American Society for Pharmacology and Experimental Therapeutics
Pharmacokinetics and Metabolism of Nateglinide in Humans
