The (R)-omeprazole hydroxylation index reflects CYP2C19 activity in healthy Japanese volunteers.

Purpose: Omeprazole has (R)- and (S)-enantiomers, which exhibit different pharmacokinetics (PK) among patients with cytochrome P450 (CYP) 2C19 genotype groups. The aim of this study was to investigate whether the 1-point, 4-h postdose (R)-omeprazole hydroxylation index (HI) of racemic omeprazole reflects the three CYP2C19 genotype groups in Japanese individuals.

Methods: Ninety healthy Japanese individuals were enrolled and classified into the three different CYP2C19 genotype groups: homozygous extensive metabolizers (hmEMs; n = 34), heterozygous EMs (htEMs; n = 44), and poor metabolizers (PMs; n = 12).

Effect of renal impairment on the pharmacokinetics of memantine.

The effect of renal impairment on the pharmacokinetics of a single oral dose of memantine (10 mg) was determined in Japanese subjects. Subjects were assigned to four groups based on baseline creatinine clearance (CL(CR)): normal renal function (> 80 mL/min, n = 6), and mild (50 to ≤ 80 mL/min, n = 6), moderate (30 to < 50 mL/min, n = 6), and severe renal impairment (5 to < 30 mL/min, n = 7). Mean memantine maximum plasma concentration (C(max)) was similar in the groups (12.

Hydroxylation of R(+)- and S(-)-omeprazole after racemic dosing are different among the CYP2C19 genotypes.

Purpose: To elucidate the stereoselective pharmacokinetics of omeprazole enantiomers and their metabolites after racemic IV dosing because there is little information about the stereoselective metabolism of omeprazole in in vivo study.

Methods: Seventeen subjects were classified into three CYP2C19 groups based on their genotypes: homozygous extensive metabolizers (hmEMs; n = 5), heterozygous EMs (htEMs; n = 7) and poor metabolizers (PMs; n = 5).

Results: After single IV administration of racemic omeprazole (20 mg), the mean area under the plasma concentration-time curve (AUC(0-∞)) of R(+)-omeprazole in PMs was significantly higher than that in hmEMs and htEMs, while that of S(-)-omeprazole was no significance among three genotypes because of a wide inter-individual variability.

Chiral assay of omeprazole and metabolites and its application to a pharmacokinetics related to CYP2C19 genotypes.

Studies investigating the relationship between CYP2C19 genotype and the stereoselective metabolism of omeprazole have not been reported. In the present study, we developed a simple and sensitive analytical method based on column switching reversed phase high-performance liquid chromatography (HPLC) with UV detection to determine the concentrations of (R)- and (S)-omeprazole and of its principal metabolites, (R)- and (S)-5-hydroxyomeprazole, and the non-chiral, omeprazole sulfone, in human plasma. Sample preparation involved liquid-liquid extraction with diethyl ether:dichloromethane (60:40, v/v) followed by clean-up on a TSK BSA-ODS/S column (5 μm, 10 mm × 4.

The effects of the SLCO2B1 c.1457C > T polymorphism and apple juice on the pharmacokinetics of fexofenadine and midazolam in humans.

Objective: The objective was to determine the effects of the SLCO2B1 c.1457C> T polymorphism and apple juice on the pharmacokinetics of fexofenadine and midazolam in humans.

Methods: Individuals were divided based on the genotype of SLCO2B1 c.

Enantioselective disposition of fexofenadine with the P-glycoprotein inhibitor verapamil.

Aims: The aim was to compare possible effects of verapamil, as a P-glycoprotein (P-gp) inhibitor, on the pharmacokinetics of each fexofenadine enantiomer, as a P-gp substrate.

Methods: Thirteen healthy Japanese volunteers (10 male and three female) were enrolled. In a randomized, two-phase, crossover design, verapamil was dosed 80 mg three times daily (with total daily doses of 240 mg) for 6 days, and on day 6, a single 120-mg dose of fexofenadine was administered along with an 80-mg dose of verapamil.

Passage-affected competitive regulation of osteoprotegerin synthesis and the receptor activator of nuclear factor-kappaB ligand mRNA expression in normal human osteoblasts stimulated by the application of cyclic tensile strain.

Mechanical stress application is a unique method for bone studies. We have reported regulation via the p38 mitogen-activated protein kinase (MAPK) pathway in osteoblasts under application of cyclic tensile strain (CTS), among many reports on the extracellular signal-regulated kinase (ERK) 1/2 pathway during mechanical stress, and questions remain as to the differences between our findings and those of others regarding types of MAPK activation. In the present study, osteoblasts were used after the third passage and stimulated by the application of 7%, 0.

The role of cytochrome P2C19 in R-warfarin pharmacokinetics and its interaction with omeprazole.

Previous studies reported omeprazole to be an inhibitor of cytochrome P450 (CYP) 2C19 and suggested the pharmacokinetic interaction of omeprazole with R-warfarin. The aim of this study was to compare possible effects of omeprazole on the stereoselective pharmacokinetics and pharmacodynamics of warfarin between CYP2C19 genotypes. Seventeen subjects, of whom 10 were homozygous extensive metabolizers (hmEMs) and seven were poor metabolizers (PMs) for CYP2C19, were enrolled in this randomized crossover study, and they ingested 20 mg omeprazole or placebo once daily for 11 days.

The different effects of itraconazole on the pharmacokinetics of fexofenadine enantiomers.

What Is Already Known About This Subject: Recently, we have shown that the plasma concentration of R-fexofenadine is greater than that of the S-enantiomer. Although itraconazole co-administration is known to increase the bioavailability of a racemic mixture of fexofenadine, little is known about the stereoselective inhibition of P-gp activity by itraconazole.

What This Study Adds: This study indicates that the stereoselective pharmacokinetics of fexofenadine are due to P-gp-mediated transport and its stereoselectivity is altered by itraconazole, a an inhibitor of P-gp.

Chemosensitivity determinants of irinotecan hydrochloride in hepatocellular carcinoma cell lines.

Irinotecan hydrochloride (CPT-11) is an effective anticancer drug, and its metabolic pathway has been well studied. Nevertheless, in human hepatocellular carcinoma (HCC), its cytotoxicity is less well studied and the determination of its chemosensitivity is unclear. We, therefore, examined chemosensitivities of HCC cell lines for CPT-11 and SN-38, and mRNA expressions of several molecules in their metabolic pathway.

Limited frequency of the CYP2C19*17 allele and its minor role in a Japanese population.

What Is Already Known About This Subject: A novel CYP2C19 gene variant, CYP2C19*17, is associated with increased metabolic activity. Ethnic differences in the frequency of the variant allele have been reported. However, the frequency of the CYP2C19*17 allele has not been studied in the Japanese population.

Estimation of the area under the concentration-time curve of racemic lansoprazole by using limited plasma concentration of lansoprazole enantiomers.

Objective: The purpose of this study was to identify the common time point that gives plasma concentrations of lansoprazole enantiomers that adequately reflect the AUC of racemic lansoprazole.

Methods: A randomized, double-blind, placebo-controlled, crossover study in three phases was conducted at intervals of 2 weeks. Eighteen healthy Japanese volunteers, including three CYP2C19 genotype groups, took a single 60-mg oral dose of lansoprazole after 6 days of pretreatment, with either clarithromycin (800 mg/day), fluvoxamine (50 mg/day), or a placebo.

Effects of the CYP3A5 genotype on omeprazole sulfoxidation in CYP2C19 PMs.

Objective: Omeprazole is metabolized by the two cytochrome P450 isoforms, CYP3A (sulfoxidation) and CYP2C 19 (hydroxydation). The aim of this study was to determine whether the CYP3A5 genotype is an important determinant of inter-individual variability of total CYP3A activity in vivo.

Methods: Plasma levels of omeprazole and omeprazole sulfone were analyzed by high-performance liquid chromatography in blood samples drawn 4-5 h after 43 CYP2C19 poor metabolizers (PMs) had ingested a single oral 40 mg dose of omeprazole.

Estimation of CYP2C19 activity by the omeprazole hydroxylation index at a single point in time after intravenous and oral administration.

Objective: The purpose of this study was to identify the common time point to achieve hydroxylation index (HI: omeprazole plasma concentration/5-hydroxyomeprazole plasma concentration) reflecting AUCOPZ/AUC5OH-OPZ after intravenous (IV) and oral (PO) administration.

Methods: Twenty young and 28 elderly healthy subjects, including different CYP2C19 genotypes, were enrolled in the study. The young subjects received either 40 mg PO or 20 mg IV omeprazole, whereas the elderly subjects received 10 mg IV.

Simultaneous determination of warfarin enantiomers and its metabolite in human plasma by column-switching high-performance liquid chromatography with chiral separation.

A simple and sensitive column-switching high-performance liquid chromatographic method for the simultaneous determination of warfarin enantiomers and their metabolites, 7-hydroxywarfarin enantiomers, in human plasma is described. Warfarin enantiomers, 7-hydroxywarfarin enantiomers, and an internal standard, diclofenac sodium, were extracted from 1 mL of a plasma sample using diethyl ether-chloroform (80:20, v/v). The extract was injected onto column I (TSK precolumn BSA-C8, 5 microm, 10 mm x 4.

Pharmacokinetics of fexofenadine enantiomers in healthy subjects.

Fexofenadine, a substrate of P-glycoprotein and an organic anion transporter polypeptide, is commonly used to assess P-glycoprotein activity in vivo. The purpose of this study was to elucidate the pharmacokinetics of each fexofenadine enantiomer. After a single oral dose of racemic fexofenadine (60 mg), the plasma and urine concentrations of fexofenadine enantiomers were measured over the course of 24 h in six healthy subjects.

Absolute bioavailability and metabolism of omeprazole in relation to CYP2C19 genotypes following single intravenous and oral administrations.

Objective: The aim of this study was to evaluate the absolute bioavailability and the metabolism of omeprazole following single intravenous and oral administrations to healthy subjects in relation to CYP2C19 genotypes.

Methods: Twenty subjects, of whom 6 were homozygous extensive metabolizers (hmEMs), 8 were heterozygous EMs (htEMs) and 6 were poor metabolizers (PMs) for CYP2C19, were enrolled in this study. Each subject received either a single omeprazole 20 mg intravenous dose (IV) or 40 mg oral dose (PO) in a randomized fashion during 2 different phases.

A developed determination of midazolam and 1'-hydroxymidazolam in plasma by liquid chromatography-mass spectrometry: application of human pharmacokinetic study for measurement of CYP3A activity.

This paper describes sensitive and reliable determination of midazolam (MDZ) and its major metabolite 1'-hydroxymidazolam (1-OHMDZ) in human plasma by liquid chromatography-mass spectrometry (LC-MS) with a sonic spray ionization (SSI) interface. MDZ, 1-OHMDZ and diazepam as an internal standard were extracted from 1ml of alkalinized plasma using n-hexane-chloroform (70:30, v/v). The extract was injected into an analytical column (YMC-Pak Pro C(18), 50mmx2.

Determination of fexofenadine enantiomers in human plasma with high-performance liquid chromatography.

A simple and sensitive high-performance liquid chromatography (HPLC) method was developed as an assay for fexofenadine enantiomers in human plasma. Fexofenadine enantiomers were separated using a mobile phase of 0.5% KH(2)PO(4)-acetonitrile (65:35, v/v) on a Chiral CD-Ph column at a flow rate of 0.

Lack of dose-dependent effects of itraconazole on the pharmacokinetic interaction with fexofenadine.

The aim of this study was to determine the inhibitory effect of itraconazole at different coadministered doses on fexofenadine pharmacokinetics. In a randomized four-phase crossover study, 11 healthy volunteers were administered a 60-mg fexofenadine hydrochloride tablet alone on one occasion (control phase) and with three different doses of 50, 100, and 200 mg of itraconazole simultaneously on the other three occasions (itraconazole phase). Although the elimination half-life and the renal clearance of fexofenadine remained relatively constant, a single administration of itraconazole with fexofenadine significantly increased mean area under the plasma concentration-time curve (AUC(0-infinity)) of fexofenadine (1701/3554, 4308, and 4107 ng h/ml for control; 50 mg, 100 mg, and 200 mg of itraconazole, respectively).

Identification of the time-point which gives a plasma rabeprazole concentration that adequately reflects the area under the concentration-time curve.

Objective: The purpose of this study is to evaluate whether a simple formula using limited blood samples can predict the area under the plasma rabeprazole concentration-time curve (AUC) in co-administration with CYP inhibitors.

Methods: A randomized double-blind placebo-controlled crossover study design in three phases was conducted at intervals of 2 weeks. Twenty-one healthy Japanese volunteers, including three CYP2C19 genotype groups, took a single oral 20-mg dose of rabeprazole after three 6-day pretreatments, i.

Pharmacokinetics of low-dose nedaplatin and validation of AUC prediction in patients with non-small-cell lung carcinoma.

Purpose: The aim of this study was to determine the pharmacokinetics of low-dose nedaplatin combined with paclitaxel and radiation therapy in patients having non-small-cell lung carcinoma and establish the optimal dosage regimen for low-dose nedaplatin. We also evaluated predictive accuracy of reported formulas to estimate the area under the plasma concentration-time curve (AUC) of low-dose nedaplatin.

Patients And Methods: A total of 19 patients were administered a constant intravenous infusion of 20 mg/m(2) body surface area (BSA) nedaplatin for an hour, and blood samples were collected at 1, 2, 3, 4, 6, 8, and 19 h after the administration.

Sensitive determination of itraconazole and its active metabolite in human plasma by column-switching high-performance liquid chromatography with ultraviolet detection.

A simple and sensitive column-switching high-performance liquid chromatographic method for the simultaneous determination of itraconazole (ITZ) and its active metabolite, hydroxyitraconazole (HIT) in human plasma is described. ITZ, HIT, and an internal standard, R051012, were extracted from 1 mL of alkalinized plasma sample using n-heptane-chloroform (60:40, vol/vol). The extract was injected onto column I (TSK precolumn BSA-ODS/S, 5 microm, 10 x 4.