Chizuko Nakamura

Determination of R(+)- and S(–)-Lansoprazole Using Chiral Stationary-Phase Liquid Chromatography and Their Enantioselective Pharmacokinetics in Humans

AbstractPurpose. Stereoselective and sensitive methods employing chiral stationary phase columns for HPLC determination of enantiomers of lansoprazole in the human serum were developed and pharmacokinetic behaviors of the enantiomers were evaluated in seven subjects. Methods. Five chiral stationary phase columns: Chiralcel OD (cellulose tris(3,5-dimethyl-phenylcarbamate)), OF (cellulose tris(4-chloro-phenylcarbamate)), OG (cellulose tris(4-methylphenylcarbamate)) and OJ (cellulose tris(4-methylbenzoate)), and Chiralpak AS (amylose tris ((S)-1 -phenylethylcarbamate)) were investigated. Results. Chiralcel OD and Chiralpak AS columns gave a good resolution of R(+)- and S(–)-enantiomers from racemic lansoprazole, but Chiralcel OF, OG, and OJ did not. The mean Cmax and the AUC values of R(+)-enantiomer were 3–5 times greater than those of S(–)-enantiomer following oral administration of 30 mg of racemic lansoprazole. The CLtot values of R(+)-enantiomer were significantly smaller than those of S(–)-enantiomer. Binding of R(+)-enantiomer to human serum proteins was significantly greater than that of S(–)-enantiomer. The mean metabolic ratio (metabolites/parent compound) in human liver microsomes of S(–)-enantiomer was significantly greater than that of R(+)-enantiomer. Conclusions. The stereoselective pharmacokinetics of lansoprazole enantiomers is likely due to its Stereoselective protein binding and/ or metabolism.

Genetic polymorphism of CYP2C19 and lansoprazole pharmacokinetics in Japanese subjects

AbstractObjective: We investigated whether interindividual differences in the pharmacokinetic disposition of lansoprazole are attributed to the genetic polymorphism of CYP2C19 which occurred by two mutations, CYP2C19m1 and CYP2C19m2, in 20 Japanese subjects. Methods: Polymerase chain reaction (PCR) restriction fragment length polymorphism procedures were used to detect the CYP2C19m1 mutation in exon 5 and the CYP2C19m2 mutation in exon 4 using SmaI and BamHI, respectively. Results: Ten subjects were homozygous (wt/wt subjects) for the wt allele in both exon 5 and exon 4, four subjects were heterozygous (wt/m1) for the CYP2C19m1 mutation, and two subjects were heterozygous (wt/m2) for the CYP2C19m2. The remaining four subjects had both mutated alleles in CYP2C19 genes, i.e., two were homozygous (m1/m1) for the defect in exon 5 and two were heterozygous (m1/m2) for the two defects in exons 5 and 4. The subjects in group 1 (wt/wt, wt/m1 and wt/m2) were the extensive metabolizers (EMs) for 5-hydroxylation of lansoprazole and were in the range of hydroxylation indexes from 3.83 to 19.8, whereas the subjects in group 2 (m1/m1 and m1/m2) were the poor metabolizers (PMs) and the indexes were in the range of 38.5 to 47.6. In group 2, AUC, t1/2 and CL/f of lansoprazole were significantly greater, longer, and lower, respectively, than those in group 1. Conclusion: The hydroxylation of lansoprazole to 5-hydroxylansoprazole was apparently impaired in the subjects with the genetic defects of CYP2C19 (m1/m1 or m1/m2).

High-performance liquid chromatographic assay for the simultaneous determination of lansoprazole enantiomers and metabolites in human liver microsomes

In this study, a simple, sensitive and enantioselective HPLC method was developed for the simultaneous determination of lansoprazole enantiomers: a proton pump inhibitor, and its major metabolites: 5-hydroxylansoprazole and lansoprazole sulfone in human liver microsomes. After extraction from the microsomal incubation mixture with a diethyl etherdichloromethane (7:3, v/v) mixture, analytes were measured by reversed-phase HPLC on a Chiralcel OD-R column. Detection was made using an ultraviolet absorbance detector set at a wavelength of 285 nm. The mobile phase consisted of a methanol-water (75:25, v/v) mixture. At a flow-rate of 0.5 ml/min, the total run time was 35 min. The limit of quantification for both lansoprazole enantiomers was 0.25 microM and for the metabolites 0.13 microM. The method is suitable for the analysis of lansoprazole enantiomers and its metabolites from human microsomal liver incubations.

Delayed-release tablets using hydroxyethylcellulose as a gel-forming matrix

Abstract Delayed-release tablets containing diltiazem hydrochloride (DIL) were prepared by using CM-type hydroxyethylcellulose (HEC) of three viscosity grades. The tablets consisted of a core containing 30 mg of DIL and an outer shell formed by compressing HEC. DIL in the core was rapidly released from the tablets after a lag time of several hours in all cases. The lag time to the start of release of DIL was more prolonged with an increase in viscosity of CM-type HEC. The rate of water-uptake was greater in the CM-L4 type HEC tablet of a low viscosity grade (14 cps) than those in CM-L3 and CM-L2 type HEC (27 and 95 cps, respectively) tablets. There was little difference in lag time to the start of release of DIL from CM-type HEC tablets between JP XII 1st (pH 1.2) and 2nd (pH 6.8) fluids. A human volunteer study was performed using the delayed-release tablets prepared with CM-type HEC of two or three viscosity grades. The t max and MRT values of CM-type HEC tablets were significantly increased with an increase in viscosity of HEC and showed only small variations between subjects, respectively. On the other hand, although the AUC values were almost the same, the C max values decreased with prolongation of lag time. The lag time in vivo for appearance of DIL in the blood corresponded well to the lag time in vitro for drug release, but tended to be shortened as compared with the lag time in vitro. These results indicate that the lag time can be optionally controlled by selecting HEC with a proper viscosity and/or by changing the amount of HEC forming the outer shell. This delayed-release tablet using HEC will be useful for control of time-related symptoms which need time-controlled or site-specific delivery in the gastrointestinal tract.

Characteristic difference in gastrointestinal excretion of clarithromycin and roxithromycin

Excretion characteristics of two new macrolides; clarithromycin and roxithromycin, into the intestinal and the gastric lumens was studied by in situ single‐pass perfusion and loop methods in rats. Roxithromycin maintained higher serum levels than clarithromycin after their intravenous administrations at a dose of 5 mg kg−1 each. Radioactivities of clarithromycin and roxithromycin exsorbed into the intestinal lumen were 8.6 and 18.9% of dose in 2 h, respectively, whereas clarithromycin and roxithromycin excreted into the bile were 28.4 and 5.9%, respectively. These results suggest that roxithromycin is transported mainly by exsorption across the intestinal membrane, whereas clarithromycin mainly by excretion through the biliary tract. On the other hand, radioactivities of clarithromycin and roxithromycin exsorbed into the gastric lumen were much less then those into the intestinal lumen and were 0.72 and 1.34% of dose in 4 h, respectively. Thus, the exsorption into the gastric lumen seems to be a minor route for the elimination of both macrolides. Consequently, the transport into the intestinal lumen via the intestinal membrane and/or the bile tract may play a significant role in the overall elimination of both macrolides.

Stereoselective analysis of the disposition of tosufloxacin enantiomers in man

SummaryThe pharmacokinetics of tosufloxacin enantiomers after oral administration of racemic tosufloxacin were examined in healthy volunteers. Only small differences were observed in time to peak concentration (2.6±0.3 [mean ± SEM] h for (+)-tosufloxacin vs 2.4±0.2 h for (−)-tosufloxacin), elimination half-life (3.61±0.24 h vs 3.49±0.23 h), and area under the curve (2.78±0.19 h·μg/ml vs 2.87±0.19 h·μg/ml); however, peak concentration (0.40±0.03 μg/ml vs 0.44±0.03 μg/ml), renal clearance (226±10 ml/min vs 202±10 ml/min), and urinary recovery (35.4±2.2% vs 32.4±1.9%) differed significantly between enantiomers.

Protective Effect of N-Benzoyl-β-Alanine Against Cisplatin Nephrotoxicity in Rats

Prophylactic effects of N-benzoyl-beta-alanine (betamipron, BP), one of a series of N-acyl amino acids, were examined against cisplatin-induced nephrotoxicity. Male Wistar rats were injected i.p. with 6 mg/kg of cisplatin combined with an i.p. BP dose given at various times and various doses. Rats were sacrificed 5 days after cisplatin injection to weigh the kidney and liver, and to determine blood urea nitrogen (BUN) and serum creatinine (serum Cr) levels. Preliminary results suggest that treatment with BP is an effective means of protection against cisplatin-induced nephrotoxicity. Combination with BP reduced the weight loss following treatment with cisplatin. The ratios of the kidney and liver weights to the body weight in the animals treated with cisplatin followed later with BP are significantly different (p < 0.05) from those in the animals that received only cisplatin. The BUN and serum Cr levels in the animals treated with cisplatin followed from -1 to 4 hr, and from -4 to 4 hr later with 250 mg/kg BP dose and followed 1 hr later with from 250 to 1000 mg/kg, and from 250 to 2000 mg/kg BP doses differed significantly (p < 0.05) from those in the animals that received only cisplatin. Histological analysis of the kidneys confirmed the protective effect of BP.

Protective Effects of Betamipron on Renal Toxicity During Repeated Cisplatin Administration in Rats and Protective Mechanism

The protective effects of betamipron (BP, N-benzoyl-beta-alanine) against nephrotoxicity induced by repeated cisplatin injections were examined. The ratio of the kidney weight to body weight and the lipid peroxide level after treatment with cisplatin plus BP tended to be larger and lower than those after treatment with cisplatin plus alkaline solution, respectively. The blood urea nitrogen, serum creatinine and glutathione levels in the animals treated with cisplatin plus BP differed significantly from those in the animals treated with cisplatin plus alkaline solution. Furthermore, the mechanism of the preventive effects of BP was analyzed for cisplatin-induced nephrotoxicity. The concentration of cisplatin in the renal cortex significantly decreased with concomitant BP. BP inhibited the uptake of cisplatin into the renal cortex in a competitive manner in the same way as an anionic transport inhibitor, probenecid. The treatment with BP appears to be useful for the renal toxicity induced by repeated cisplatin administration.

Betamipron reduces cisplatin nephrotoxicity in rodents without modifying its antileukemic activity in mice.

Protective effects of betamipron (BP, N-benzoyl-beta-alanine), one of a series of N-acyl amino acids, on cisplatin-induced nephrotoxicity were examined. Since the damage observed in the kidney is localized to the proximal tubule cells, we investigated the influence of BP on urinary enzymes and excreta. Male Wistar rats and ddY mice were injected i.p. with 6 mg/kg and 16 mg/kg, respectively, of cisplatin combined with an i.p. 250 mg/kg BP dose. The toxicity of cisplatin as indicated by body weight gain, blood urea nitrogen, and serum creatinine levels was significantly (p < 0.05) suppressed by administration of BP after cisplatin treatment. The increase in urinary N-acetyl-beta-D-glucosaminidase activity, increase and subsequent decrease in gamma-glutamyl transferase activities, and increase in beta 2-microglobulin level observed after treatment with cisplatin were suppressed by administration of BP after cisplatin treatment. The combination of cisplatin and BP had no apparent effect on the efficacy of cisplatin against P388 leukemic cells in mice.

Changes in mucosal phospholipid-related protection in some gastric diseases

Background:  Phospholipids play an important role in gastric mucosal protection. The purpose of the present study was to investigate changes in various phospholipids in the fundic and pyloric gland mucosae of patients with gastric mucosal disease.